Patent Publication Number: US-2021161750-A1

Title: Leg brace, leg brace unit, and lower-limb system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese patent application No. 2019-215429, filed on Nov. 28, 2019, the disclosure of which is incorporated herein in its entirety by reference. 
     BACKGROUND 
     The present disclosure relates to a leg brace, a leg brace unit, and a lower-limb system. 
     Knee osteoarthritis in which due to deterioration of cartilage or wear thereof in a knee joint, a pain is caused in the knee joint during walking has been know. 
     In the early stage of knee osteoarthritis, walking on level ground does not cause a problem, but the patient may feel a pain in his/her knee when he/she goes up and down stairs. Alternatively, the patient does not feel a pain in his/her knee during walking, but he/she cannot sit down in the Japanese “seiza” style (i.e., cannot sit on his/her heels) because of a pain in the knee joint. 
     As the knee osteoarthritis progresses, both legs become O-shaped bowlegs or X-shaped bowlegs. As a result, the burden on the knee joint increases due to the wear of the cartilage and hence the knee joint becomes arthritic. Further, because of the arthritis, mere bending and stretching of the knee joint become painful. Therefore, the patient has a difficulty in not only going up and down stairs, but also walking on level ground. 
     Further, as the knee osteoarthritis progresses even further, the cartilage disappears (i.e., is completely worn out) and the thighbone and the shinbone directly rub against each other, thus causing a severe pain. 
     As a known method for surgically treating knee osteoarthritis, there is total knee replacement in which a knee joint is replaced with an artificial material made of metal or resin. As a known method for non-surgically treating knee osteoarthritis, an anti-inflammatory analgesic may be administered. 
     Published Japanese Translation of PCT International Publication for Patent Application, No. 2018-518318 discloses an artificial knee including a thigh link fixed to a thigh of a user, a shin link fixed to a shin thereof, and a passive compressive force generator that resists bending of the shin link with respect to the thigh link. The passive compressive force generator is, for example, an air spring or a compression coil spring. 
     SUMMARY 
     One of the objects of the present disclosure is to provide a technique for alleviating a pain in a knee joint of a patient suffering from knee osteoarthritis. 
     A first exemplary aspect is a leg brace configured to be attached to a leg of a user, including: an inner thigh link configured to be attached to an inner side of a thigh of the leg; an inner lower-leg link rotatably connected to the inner thigh link, and configured to be attached to an inner side of a lower leg of the leg; inner extension force generation means for generating an inner extension force between the inner thigh link and the inner lower-leg link in a direction in which a knee joint of the leg extends; an outer thigh link configured to be attached to an outer side of the thigh of the leg; an outer lower-leg link rotatably connected to the outer thigh link, and configured to be attached to an outer side of the lower leg of the leg; and outer extension force generation means for generating an outer extension force between the outer thigh link and the outer lower-leg link in a direction in which the knee joint of the leg extends, in which the inner extension force is stronger than or weaker than the outer extension force. According to the above-described configuration, it is possible, when the leg to which the leg brace is attached becomes a stance state, to guide the center of gravity of the user to the weaker one of the inner extension force side and the outer extension force side, and thereby to alleviate a pain caused by knee osteoarthritis. 
     The inner extension force may be stronger than the outer extension force. According to the above-described configuration, it is possible, when the leg to which the leg brace is attached becomes the stance state, to guide the center of gravity of the user toward the outer side, and thereby to alleviate a pain caused by knee osteoarthritis when the leg is an O-shaped bowleg. 
     The inner extension force may be weaker than the outer extension force. According to the above-described configuration, it is possible, when the leg to which the leg brace is attached becomes the stance state, to guide the center of gravity of the user toward the inner side, and thereby to alleviate a pain caused by knee osteoarthritis when the leg is an X-shaped bowleg. 
     The inner extension force generation means and the outer extension force generation means may include a spring or a damper. 
     The inner extension force generation means and the outer extension force generation means may include a spring configured so that its spring constant is adjustable. 
     The inner extension force generation means and the outer extension force generation means may include a damper configured so that its damping coefficient is adjustable. 
     A second exemplary aspect is a leg brace configured to be attached to a leg of a user, including: a thigh link configured to be attached to a thigh of the leg; a lower-leg link rotatably connected to the thigh link, and configured to be attached to a lower leg of the leg; and extension force generation means for generating an extension force between the thigh link and the lower-leg link in a direction in which a knee joint of the leg extends, in which the thigh link and the lower-leg link form a link unit, and the link unit is disposed only on one of an inner side and an outer side of the leg. According to the above-described configuration, it is possible, when the leg on which the leg brace is attached becomes a stance state, to guide the center of gravity of the user toward the side opposite to the side on which the link unit is disposed, and thereby to alleviate a pain caused by knee osteoarthritis. 
     The link unit may be disposed on an inner side of the leg. According to the above-described configuration, it is possible, when the leg to which the leg brace is attached becomes the stance state, to guide the center of gravity of the user toward the outer side, and thereby to alleviate a pain caused by knee osteoarthritis when the leg is an O-shaped bowleg. 
     The link unit may be disposed on an outer side of the leg. According to the above-described configuration, it is possible, when the leg to which the leg brace is attached becomes the stance state, to guide the center of gravity of the user toward the inner side, and thereby to alleviate a pain caused by knee osteoarthritis when the leg is an X-shaped bowleg. 
     A third exemplary aspect is a leg brace unit including a pair of leg braces each of which is attached to a respective one of legs of a user, in which each of the leg braces includes: a thigh link configured to be attached to a thigh of a corresponding leg; a lower-leg link rotatably connected to the thigh link, and configured to be attached to a lower leg of the corresponding leg; and extension force generation means for generating an extension force between the thigh link and the lower-leg link in a direction in which a knee joint of the leg extends, and an extension force of one of the leg braces is stronger than or weaker than that of the other leg brace. According to the above-described configuration, it is possible to guide the center of gravity of the user to the side on which the extension force is weaker, and thereby to alleviate a pain caused by knee osteoarthritis. 
     A fourth exemplary aspect is a lower-limb system including: a brace main body configured to be attached to a lower limb of a user; a load removal detection unit configured to detect that a load exerted on the lower limb is removed; force-applying means capable of applying a force to the brace main body in a direction in which the brace main body recedes from a ground surface; and a control unit configured to control the force-applying means so that when the load exerted on the lower limb is removed, the force-applying means applies the force to the brace main body in the direction in which the brace main body recedes from the ground surface. According to the above-described configuration, it is possible to guide the center of gravity of the user toward the lower limb opposite to the lower limb to which the lower-limb brace is attached, and thereby to alleviate a pain in the lower limb opposite to the lower limb to which the lower-limb brace is attached caused by knee osteoarthritis of that lower limb when that leg is an O-shaped bowleg. 
     According to the present disclosure, it is possible to alleviate a pain in a knee joint of a patient suffering from knee osteoarthritis. 
     The above and other objects, features and advantages of the present disclosure will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a knee joint weight-bearing apparatus (First Embodiment); 
         FIG. 2  is a schematic side view of a knee joint weight-bearing apparatus when the knee joint is stretched (First Embodiment); 
         FIG. 3  is a schematic side view of the knee joint weight-bearing apparatus when the knee joint is bent (First Embodiment); 
         FIG. 4  shows a state in which a user sits on a chair while wearing the knee joint weight-bearing apparatus (First Embodiment); 
         FIG. 5  is a schematic front view of a leg brace (Second Embodiment); 
         FIG. 6  is a side view of force-applying means of the leg brace (Second Embodiment); 
         FIG. 7  is a schematic front view showing a leg brace attached to a diseased leg in the case where the diseased leg is an O-shaped bowleg (Third Embodiment); 
         FIG. 8  is a schematic front view showing a leg brace attached to a diseased leg in the case where the diseased leg is an X-shaped bowleg (Fourth Embodiment); 
         FIG. 9  is a schematic front view showing leg braces each of which is attached a respective one of both legs in the case where the legs are O-shaped bowlegs (Fifth Embodiment); and 
         FIG. 10  is a schematic front view showing a lower-limb brace attached to a diseased leg in the case where the diseased leg is an O-shaped bowleg (Sixth Embodiment). 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
     A first embodiment according to the present disclosure will be described hereinafter with reference to  FIGS. 1 to 4 . 
       FIG. 1  shows a knee joint weight-bearing apparatus  2  which is attached to a leg  1  of a user when it is used. The knee joint weight-bearing apparatus  2  is typically used while being attached to one of the two legs  1  of the user in which the user suffers from knee osteoarthritis. However, one knee joint weight-bearing apparatus  2  may be attached to each of both legs  1 . 
     The knee joint weight-bearing apparatus  2  is an apparatus that, by being attached to the leg  1  of the user, relieves a part or the whole of the load (e.g., the weight) exerted on the knee joint  3  of the leg  1 . In this embodiment, by being attached to the leg  1  of the user, the knee joint weight-bearing apparatus  2  relieves a part of the load exerted on the knee joint  3  of the leg  1 . 
     As being well known, the leg  1  includes a thigh  4 , a lower leg  5 , and a foot  6 . A buttock  7  is positioned above the leg  1 . The knee joint  3  is a joint that connects the thigh  4  with the lower leg  5 . 
     The knee joint weight-bearing apparatus  2  includes a buttock attaching part  8 , a lower-leg attaching part  9 , and two thigh connection units  10 . The knee joint weight-bearing apparatus  2  further includes a foot attaching part  11 . 
     In the following description, a front/rear direction and a left/right direction are defined based on the orientation of the body of the user. A forward direction may be defined as the normal walking direction of the user. The left/right direction may be defined as the longitudinal direction of a line segment that horizontally connects the right and the left arms. 
     Buttock Attaching Part  8   
     The buttock attaching part  8  is a part that is attached to the buttock  7  of the user and supports the buttock  7  of the user. The buttock attaching part  8  includes a buttock facing part  15 , two buttock frames  16 , and a buttock fixing band  17 . 
     The buttock facing part  15  is a part that is substantially opposed to (i.e., faces) the hipbone of the buttock  7  of the user when the user is in a stance state or a sitting position. In this embodiment, the buttock facing part  15  is positioned rearward of and below the hipbone of the user&#39;s buttock  7 . The buttock facing part  15  may has an open-cell structure such as urethane foam, or a closed-cell structure such as polyethylene foam for the purpose of dispersing a contact pressure exerted to the user. 
     The two buttock frames  16  are arranged so as to sandwich the user&#39;s thigh  4  in the left/right direction of the user. Each of the buttock frames  16  is fixed to the buttock facing part  15  by, for example, a screw and extends forward from the buttock facing part  15 . Each of the buttock frames  16  horizontally extends substantially in a straight line along the front/rear direction of the user when the user is in the stance state. It can be expressed that the two buttock frames  16  are connected to each other by the buttock facing part  15 . Each of the buttock frames  16  includes a front thigh link upper end connection part  16   a  and a rear thigh link upper end connection part  16   b . The front thigh link upper end connection part  16   a  is positioned forward of the rear thigh link upper end connection part  16   b.    
     The buttock fixing band  17  is a band for fixing the buttock attaching part  8  to the base of the user&#39;s thigh  4 , and is disposed between the two buttock frames  16 . The buttocks fixing band  17  is disposed so as to connect two buttocks frames  16  with each other. The buttock fixing band  17  is disposed on the opposite side to the buttock facing part  15  across the user&#39;s thigh  4 . By the above-described configuration, the user can appropriately attach the buttock attaching part  8  to his/her buttock  7  by adjusting the band length of the buttock fixing band  17  according to the thickness of the base of the user&#39;s thigh  4 . 
     Lower-leg Attaching Part  9   
     The lower-leg attaching part  9  is a part that is attached to the lower leg  5  of the user. The lower-leg attaching part  9  includes two lower-leg facing parts  20  and a lower-leg fixing band  21 . 
     The two lower-leg facing parts  20  are arranged so as to sandwich the user&#39;s lower leg  5  in the left/right direction. Each of the lower-leg facing parts  20  vertically extends along the lower leg  5 . A thigh link connection part  22 , to which a respective one of the thigh connection units  10  is connected, is formed at the upper end of each of the lower-leg facing parts  20 . 
     The thigh link connection part  22  includes a front thigh link lower end connection part  22   a  and a rear thigh link lower end connection part  22   b . The front thigh link lower end connection part  22   a  is positioned forward of and above the rear thigh link lower end connection part  22   b . The front thigh link lower end connection part  22   a  is positioned at roughly the same height as the user&#39;s knee joint  3  when the user is in the standing state. The rear thigh link lower end connection part  22   b  is positioned below the user&#39;s knee joint  3  when the user is in the standing state. Specifically, when the height of the user is represented by HT, the rear thigh link lower end connection part  22   b  is disposed at a position that is lower than the user&#39;s knee joint  3  by a length HT*0.1 to HT*0.15 when the user is in the standing state. 
     The lower end of each of the lower-leg facing parts  20  is rotatably connected to the foot attaching part  11 . 
     Foot Attaching Part  11   
     The foot attaching part  11  is a part that is fixed to the foot  6  of the user. As shown in  FIG. 1 , like a sandal, the foot attaching part  11  may include a sole part  30  that is opposed to (i.e., faces) the sole of the foot  6 , a foot fixing band  31  that is opposed to (i.e., faces) the instep of the foot  6 , and two foot projecting parts  32 . The user can appropriately attach the foot attaching part  11  to his/her foot  6  by putting the foot  6  between the sole part  30  and the foot fixing band  31  and adjusting the band length of the foot fixing band  31 . The two foot projecting parts  32  project upward from the sole part  30  so as to sandwich the foot  6  in the left/right direction. The lower end of each of the lower-leg facing parts  20  of the lower-leg attaching part  9  is rotatably connected to the upper end of a respective one of the leg projecting parts  32  of the leg attaching part  11 . Note that the foot attaching part  11  may be formed like a boot, a sneaker, a leather shoe, or a slip-on, instead of being formed like a sandal. For example, when the foot attaching part  11  is formed like a boot, the lower end of each of the lower-leg facing parts  20  of the lower-leg attaching part  9  is rotatably connected to one (or some) of the components constituting the boot. 
     Thigh Connecting Unit  10   
     The two thigh connection units  10  are arranged so as to sandwich the user&#39;s thigh  4  in the left/right direction. Each of the thigh connection units  10  extends in the vertical direction when the user is in the standing state. Each of the thigh connection units  10  connects the buttock attaching part  8  with the lower-leg attaching part  9 . Details of the thigh connection units  10  are described hereinafter. 
     Each of the thigh connection units  10  includes a front thigh link  40  and a rear thigh link  41 . The front thigh link  40  connects the buttock attaching part  8  with the lower-leg attaching part  9 . The rear thigh link  41  also connects the buttock attaching part  8  with the lower-leg attaching part  9 . The rear thigh link  41  is disposed rearward of the front thigh link  40 . The longitudinal directions of the front and rear thigh links  40  and  41  are roughly parallel to each other. The front and rear thigh links  40  and  41  extend roughly vertically when the user is in the standing state. 
     The upper end of the front thigh link  40  of each of the thigh connection units  10  is rotatably connected to the front thigh link upper end connection part  16   a  of a respective one of the buttock frames  16  of the buttock attaching part  8 . The lower end of the front thigh link  40  of each of the thigh connection units  10  is rotatably connected to the front thigh link lower end connection part  22   a  of the thigh link connection part  22  of a respective one of the lower leg facing parts  20  of the lower-leg attaching part  9 . 
     The upper end of the rear thigh link  41  of each of the thigh connection units  10  is rotatably connected to the rear thigh link upper end connection part  16   b  of a respective one of the buttock frames  16  of the buttock attaching part  8 . The lower end of the rear thigh link  41  of each of the thigh connection units  10  is rotatably connected to the rear thigh link lower end connection part  22   b  of the thigh link connection part  22  of a respective one of the lower leg facing parts  20  of the lower-leg attaching part  9 . 
     Therefore, each of the buttock frames  16  of the buttock attaching part  8 , the front and rear thigh links  40  and  41  of a respective one of the thigh connection units  10 , and the thigh link connection part  22  constitute the so-called four-bar linkage. 
     In this embodiment, the front thigh link  40  is a string made of a flexible material, typically made of a polyamide synthetic resin such as nylon. The front thigh link  40  is formed by connecting the front thigh link upper part  40   a  with the front thigh link lower part  40   b . Further, the front thigh link  40  includes a length adjusting mechanism  42  and a detaching mechanism  43  (a front upper/lower connection part). The length adjusting mechanism  42  is a mechanism for adjusting the link length of the front thigh link  40 , i.e., the distance between the front thigh link upper end connection part  16   a  and the front thigh link lower end connection part  22   a , and is typically formed by a belt feed. In this embodiment, the length adjusting mechanism  42  adjusts the link length of the front thigh link upper part  40   a . However, instead of adjusting the link length of the front thigh link upper part  40   a , the link length of the front thigh link lower part  40   b  may be adjusted. The detaching mechanism  43  is a mechanism for temporarily detaching the front thigh link  40 , and is typically a buckle. The detaching mechanism  43  detachably connects the front thigh link upper part  40   a  with the front thigh link lower part  40   b.    
     In this embodiment, the front thigh link  40  is made of a flexible material. However, the front thigh link  40  may be made of a non-flexible material. For example, the front thigh link  40  is formed of a beam made of metal or wood. Further, specific examples of the flexible material are not limited to the above-shown synthetic resins and may include metals. In such cases, the front thigh link  40  may be a metal wire. 
     The rear thigh link  41  is composed of a rear thigh link upper part  41   a  and a rear thigh link lower part  41   b . The rear thigh link upper part  41   a  and the rear thigh link lower part  41   b  are rotatably connected to each other at a rear thigh connection part  44 . The rear thigh connection part  44  is provided with a switching snap  45  (a rear upper/lower connection part) for switching between a state in which the rear thigh link upper part  41   a  is relatively rotatable with respect to the rear thigh link lower part  41   b  and a state in which the rear thigh link upper part  41   a  is not rotatable with respect to the rear thigh link lower part  41   b . The switching snap  45  is typically a tubular member provided in the rear thigh link lower part  41   b  in such a manner that the tubular member is slidable along the rear thigh link lower part  41   b  in its longitudinal direction. In this case, when the switching snap  45  is slid upward and thereby covers both the rear thigh link upper part  41   a  and the rear thigh link lower part  41   b  at the same time, the rear thigh link  41  becomes the aforementioned non-rotatable state. Further, when the switching snap  45  is slid downward and hence does not cover the rear thigh link upper part  41   a , the rear thigh link  41  becomes the aforementioned rotatable state. The configuration of the switching snap  45  is not limited to the above-described configuration. That is, other known configurations may be adopted for the switching snap  45 . The rear thigh connection part  44  and the switching snap  45  are disposed near the knee joint  3 . 
     A gas spring  46  (resistive-force generation means) is provided in the rear thigh link upper part  41   a . The gas spring  46  is a spring using a reaction force of a compressed gas, and obtains the reaction force by filling a sealed cylinder with a nitrogen gas, which is used as the compressed gas, and compressing the gas by a piston. The gas spring  46  is configured so that the rear thigh link upper part  41   a  can extend and contract in the longitudinal direction thereof. The gas spring  46  generates a roughly constant repulsive force irrespective of the link length of the rear thigh link upper part  41   a  in the direction in which the link length of the rear thigh link upper part  41   a  increases. 
     Regarding the buttock attaching part  8 , the buttock attaching part  8  is considered to be a problem of a beam in which the buttock attaching part  8  is simply supported by the front and rear thigh link upper end connection parts  16   a  and  16   b , and distributed loads (e.g., distributed weights) are exerted downward on the buttock facing part  15 . In this case, the buttock facing part  15  is configured so that a concentrated load equivalent to downward distributed loads exerted on the buttock facing part  15  is exerted on a part of the buttock facing part  15  located rearward of the rear thigh link upper end connection part  16   b . Therefore, when the user applies a load (e.g., his/her weight) to the buttock facing part  15 , a tensile force is generated in the front thigh link  40  and a compressive force acts on the rear thigh link  41 . 
     Further, the repulsive force generated by the gas spring  46  is the resistive force itself against the above-described compressive force. 
     The above-described knee joint weight-bearing apparatus  2  is particularly suitable for knee osteoarthritis. 
     The knee osteoarthritis causes a symptom in which cartilage in a knee joint deteriorates or is worn away, causing a pain in the knee joint during walking. 
     In the early stage of knee osteoarthritis, walking on level ground surface does not cause a problem, but the patient may feel a pain in his/her knee when he/she goes up and down stairs. Alternatively, the patient does not feel a pain in his/her knee during walking, but he/she cannot sit down in the Japanese “seiza” style (i.e., cannot sit on his/her heels) because of a pain in the knee joint. 
     As the knee osteoarthritis progresses, both legs become O-shaped bowlegs or X-shaped bowlegs. As a result, the burden on the knee joint increases due to the wear of the cartilage and hence the knee joint becomes arthritic. Further, because of the arthritis, mere bending and stretching of the knee joint become painful. Therefore, the patient has a difficulty in not only going up and down stairs, but also walking on level ground surface. 
     Further, as the knee osteoarthritis progresses even further, the cartilage disappears (i.e., is completely worn out) and the thighbone and the shinbone directly rub against each other, thus causing a severe pain. 
     For a patient with knee osteoarthritis, the most direct cause of a pain in the knee joint is that the knee joint supports the weight of the upper body of the patient. Therefore, if a part or the whole of the load (e.g., the weight) exerted on the knee joint can be relieved, the pain in the knee joint can be alleviated. 
     Therefore, the knee joint weight-bearing apparatus  2  functions as an apparatus for relieving a part or the whole of the load exerted on the knee joint  3 . In this embodiment, the knee joint weight-bearing apparatus  2  functions as an apparatus for relieving a part of the load exerted on the knee joint  3 . 
     Specifically, once the knee joint weight-bearing apparatus  2  is attached to the leg  1 , the user feels, when he/she walks, as if he/she is walking while sitting on a chair at all times. Note that the buttock attaching part  8  of the knee joint weight-bearing apparatus  2  functions as a sitting surface of the chair, and both of the thigh connection units  10  and the lower-leg attaching part  9  function as legs of the chair. 
     Specific operations of the knee joint weight-bearing apparatus  2  are described hereinafter. 
     That is, as shown in  FIG. 2 , when a user applies a load P (e.g., his/her weight) to the buttock facing part  15 , this load is received by the two thigh connection units  10  and the lower-leg attaching part  9 . In this state, a compressive force acts on the rear thigh link  41  of each of the thigh connection units  10 . Meanwhile, a tensile force R acts on the front thigh link  40  of each of the thigh connection units  10 . The following relation holds: the front thigh link upper end connection part  16   a  acts as a fulcrum; the buttock facing part  15  becomes a point of force; and the rear thigh link upper end connection part  16   b  becomes a point of action. In this state, the gas spring  46  generates a resistive force Q against the compressive force acting on the rear thigh link  41 . A part of the load exerted on the user&#39;s knee joint  3  is relieved by this resistive force Q. 
     Next, as shown in  FIG. 3 , when the knee joint  3  of the leg  1  is bent, the lower leg  5  is inclined forward. Therefore, the lower-leg attaching part  9  is also inclined forward in a similar manner. In this state, since the gas spring  46  becomes moderately short, the posture of the buttock facing part  15  does not lean forward. Therefore, the user can easily continue applying the load to the buttock attaching part  8  without feeling that anything is wrong. That is, the function of the knee joint weight-bearing apparatus  2  for relieving a part of the load exerted on the user&#39;s knee joint  3  is continuously performed without causing any problem. 
     Note that as shown in  FIG. 2 , the rear thigh link lower end connection part  22   b  is disposed below the knee joint  3  and away from the knee joint  3  when the user is in the stance state. Therefore, as compared to the case where the rear thigh link lower end connection part  22   b  is disposed at the same height as the knee joint  3  when the user is in the stance state as shown by phantom lines  50  in  FIG. 3 , the inclination of the rear thigh link  41  that is caused when the knee joint  3  is bent is reduced. Therefore, the longitudinal direction of the rear thigh link  41  roughly coincides with the direction in which the user applies the load to the buttock attaching part  8 , thus providing an advantage that the user can easily apply the load to the buttock attaching part  8  along the longitudinal direction of the rear thigh link  41 . In other words, as compared to the case where the rear thigh link lower end connection part  22   b  is disposed at the same height as the knee joint  3  when the user is in the stance state as shown by the phantom lines  50  in  FIG. 3 , when the knee joint  3  is bent, the user can easily compress the gas spring  46  and hence can stabilize the posture of the buttock attaching part  8  without inclining it forward. 
       FIG. 4  shows a sitting position of a user. The sitting position means a position (i.e., a posture) in which the user sits on a chair or the like. As shown in  FIG. 4 , when a user with the knee joint weight-bearing apparatus  2  attached to his/her leg change his/her position from the stance state to the sitting position, he/she brings the rear thigh link upper part  41   a  and the rear thigh link lower part  41   b  of each of the thigh connection units  10  into a relatively rotatable state by using the switching snap  45 . In addition, he/she may detach the front thigh link upper part  40   a  from the front thigh link lower part  40   b  by using the detaching mechanism  43 . In this way, the front thigh link  40  can be bent at the rear thigh connection part  44 . To begin with, the rear thigh connection part  44  is disposed near the knee joint  3 , so that the knee joint weight-bearing apparatus  2  does not hamper the bending motion of the knee joint  3  by the user. 
     It should be noted that in the above-described first embodiment, the knee joint weight-bearing apparatus  2  is a specific example of the leg brace attached to the leg  1  of the user. 
     As shown in  FIG. 1 , the knee joint weight-bearing apparatus  2  includes an inner thigh link  41 IN attached on the inner side of the thigh  4  of the leg  1 . The inner thigh link  41 IN corresponds to the rear thigh link  41  of the thigh connection unit  10  disposed on the inner side of the thigh  4  of the leg  1 . 
     The knee joint weight-bearing apparatus  2  includes an inner lower-leg link  20 IN that is rotatably connected to the inner thigh link  41 IN, and attached on the inner side of the lower leg  5  of the leg  1 . The inner lower-leg link  20 IN corresponds to the lower leg facing part  20  disposed on the inner side of the lower leg  5  of the leg  1 . 
     The knee joint weight-bearing apparatus  2  includes an inner gas spring  46 IN that generates an inner extension force between the inner thigh link  41 IN and the inner lower-leg link  20 IN in a direction in which the knee joint  3  of the leg  1  extends. The inner gas spring  46 IN is a specific example of the inner extension force generation means. The inner gas spring  46 IN corresponds to the gas spring  46  disposed in the rear thigh link  41  of the thigh connection unit  10  disposed on the inner side of the thigh  4  of the leg  1 . As shown in  FIGS. 2 and 3 , the inner extension force corresponds to the resistive force Q generated by the gas spring  46  disposed in the rear thigh link  41  of the thigh connection unit  10  disposed on the inner side of the thigh  4  of the leg  1 . 
     Referring to  FIG. 1  again, the knee joint weight-bearing apparatus  2  includes an outer thigh link  41 OUT attached on the outer side of the thigh  4  of the leg  1 . The outer thigh link  41 OUT corresponds to the rear thigh link  41  of the thigh connection unit  10  disposed on the outer side of the thigh  4  of the leg  1 . 
     The knee joint weight-bearing apparatus  2  includes an outer lower-leg link  20 OUT that is rotatably connected to the outer thigh link  41 OUT, and attached on the outer side of the lower leg  5  of the leg  1 . The outer lower-leg link  20 OUT corresponds to the lower leg facing part  20  disposed on the outer side of the lower leg  5  of the leg  1 . 
     The knee joint weight-bearing apparatus  2  includes an outer gas spring  46 OUT that generates an outer extension force between the outer thigh link  41 OUT and the outer lower-leg link  20 OUT in a direction in which the knee joint  3  of the leg  1  extends. The outer gas spring  46 OUT is a specific example of the outer extension force generation means. The outer gas spring  46 OUT corresponds to the gas spring  46  disposed in the rear thigh link  41  of the thigh connection unit  10  disposed on the outer side of the thigh  4  of the leg  1 . As shown in  FIGS. 2 and 3 , the outer extension force corresponds to the resistive force Q generated by the gas spring  46  disposed in the rear thigh link  41  of the thigh connection unit  10  disposed on the outer side of the thigh  4  of the leg  1 . 
     Further, the inner extension force of the inner gas spring  461 N is adjusted so as to become stronger than the outer extension force of the outer gas spring  46 OUT. According to the above-described configuration, it is possible, when the leg  1  to which the knee joint weight-bearing apparatus  2  is attached becomes a stance state, to guide the center of gravity of the user to the outer side (i.e., in a direction from the inner thigh link  411 N toward the outer thigh link  41 OUT), and thereby to reduce the load exerted on the cartilage on the inner side of the knee joint  3  when the leg  1  is an O-shaped bowleg. Therefore, it is possible to alleviate a pain in the knee joint  3  caused by knee osteoarthritis. 
     The above-described first embodiment can be modified as follows. 
     That is, the inner extension force of the inner gas spring  461 N may be adjusted so as to become weaker than the outer extension force of the outer gas spring  46 OUT. According to the above-described configuration, it is possible, when the leg  1  to which the knee joint weight-bearing apparatus  2  is attached becomes a stance state, to guide the center of gravity of the user to the inner side (i.e., in a direction from the outer thigh link  41 OUT toward the inner thigh link  411 N), and thereby to reduce the load exerted on the cartilage on the outer side of the knee joint  3  when the leg  1  is X-shaped bowleg. Therefore, it is possible to alleviate the pain in the knee joint  3  caused by knee osteoarthritis. 
     As described above, by making the inner extension force stronger than or weaker than the outer extension force, it is possible, when the leg to which the knee joint weight-bearing apparatus  2  is attached becomes a stance state, to guide the center of gravity of the user to the weaker one of the inner extension force side and the outer extension force side, and thereby to alleviate a pain in the knee joint  3  caused by knee osteoarthritis. 
     Note that springs or dampers may be used as the inner extension force generation means and the outer extension force generation means. Both a spring and a damper may be used at the same time as the inner extension force generation means and the outer extension force generation means. Specific examples of the spring or the damper include a coil spring, a gas damper, an oil damper, and an oilless gas spring. 
     Further, when a spring is used as the inner extension force generation means or the outer extension force generation means, the spring may be configured so that its spring constant is adjustable. Similarly, when a damper is used as the inner extension force generation means or the outer extension force generation means, the damper may be configured so that its damping coefficient is adjustable. 
     Second Embodiment 
     Next, a second embodiment will be described with reference to  FIGS. 5 and 6 . Note that the same symbols as those used in the above-described first embodiment are used for structures, components, and parts corresponding to those in the above-described first embodiment. 
       FIG. 5  shows a leg brace  50  which is attached to a leg  1  of a user when it is used. The leg brace  50  is typically used while being attached to one of the two legs  1  of the user in which the user suffers from knee osteoarthritis. However, one leg brace  50  may be attached to each of both legs  1 . In this embodiment, the leg brace  50  is attached only to the left leg  1 L of the user as shown in  FIG. 5 . 
     The leg brace  50  is attached to the leg  1  of the user and, by doing so, reduces a pain in the knee joint  3  of the leg  1 . 
     The leg brace  50  includes an inner thigh link  51 , an inner lower-leg link  52 , and inner extension force generation means  53 . 
     The leg brace  50  includes an outer thigh link  54 , an outer lower-leg link  55 , and outer extension force generation means  56 . 
     The inner thigh link  51  is a link that is attached on the inner side of the thigh  4  of the leg  1 , and extends along the longitudinal direction of the thigh  4 . 
     The inner lower-leg link  52  is a link that is attached on the inner side of a lower leg  5  of the leg  1 , and extends along the longitudinal direction of the lower leg  5 . 
     As shown in  FIG. 6 , the inner lower-leg link  52  is connected to the inner thigh link  51  so as to be rotatable with respect thereto in the pitch direction. That is, the leg brace  50  includes an inner connection part  57  that rotatably connects the inner thigh link  51  with the inner lower-leg link  52 . 
     The inner extension force generation means  53  generates an inner extension force  58  between the inner thigh link  51  and the inner lower-leg link  52  in a direction in which the knee joint  3  of the leg  1  extends. As the inner extension force generation means  53 , it is possible to use, for example, either one of a spring and a damper that is connected to the inner thigh link  51  at one end above the inner connection part  57  and also connected to the inner lower-leg link  52  at the other end below the inner connection part  57 . As the inner extension force generation means  53 , it is also possible to use one that includes both a spring and a damper so that it exhibits the characteristics of the spring and the damper at the same time. 
     When a spring is used as the inner extension force generation means  53 , the spring may be configured so that its spring constant is adjustable. A typical example of the spring is a compression coil spring. 
     When a damper is used as the inner extension force generation means  53 , the damper may be configured so that its damping coefficient is adjustable. 
     Referring to  FIG. 5  again, the outer thigh link  54  is a link that is attached on the outer side of the thigh  4  of the leg  1 , and extends along the longitudinal direction of the thigh  4 . 
     The outer lower-leg link  55  is a link that is attached on the outer side of the lower leg  5  of the leg  1 , and extends along the longitudinal direction of the lower leg  5 . 
     As shown in  FIG. 6 , the outer lower-leg link  55  is connected to the outer thigh link  54  so as to be rotatable with respect thereto in the pitch direction. That is, the leg brace  50  includes an outer connection part  59  that rotatably connects the outer thigh link  54  with the outer lower-leg link  55 . 
     The outer extension force generation means  56  generates an outer extension force  60  between the outer thigh link  54  and the lateral lower-leg link  55  in a direction in which the knee joint  3  of the leg  1  extends. As the outer extension force generation means  56 , it is possible to use, for example, either one of a spring or a damper that is connected to the outer thigh link  54  at one end above the outer connection part  59  and also connected to the outer lower-leg link  55  at the other end below the outer connection part  59 . As the outer extension force generation means  56 , it is also possible to use one that includes both a spring and a damper so that it exhibits the characteristics of the spring and the damper at the same time. 
     When a spring is used as the outer extension force generation means  56 , the spring may be configured so that its spring constant is adjustable. A typical example of the spring is a compression coil spring. 
     When a damper is used as the outer extension force generation means  56 , the damper may be configured so that its damping coefficient is adjustable. 
     Referring to  FIG. 5  again, the inner and outer thigh links  51  and  54  are fixed to the thigh  4  by thigh fixing bands  61   a  and  61   b.    
     The inner and outer lower-leg links  52  and  55  are fixed to the lower leg  5  by lower-leg fixing bands  62   a  and  62   b.    
     Further, the inner extension force  58  is adjusted so as to become stronger than or weaker than the outer extension force  60 . According to the above-described configuration, it is possible, when the leg  1  to which the leg brace  50  is attached becomes a stance state, to guide the center of gravity of the user to the weaker one of the side of the inner extension force  58  and the side of the outer extension force  60 , and thereby to alleviate a pain in the knee joint  3  caused by knee osteoarthritis. 
     Specifically, in the case where the inner extension force  58  is stronger than the outer extension force  60 , it is possible, when the leg  1  to which the leg brace  50  is attached becomes a stance state, to guide the center of gravity of the user toward the outer side, and thereby to alleviate a pain in the knee joint  3  caused by knee osteoarthritis when the leg  1  is an O-shaped bowleg. 
     Conversely, in the case where the inner extension force  58  is weaker than the outer extension force  60 , it is possible, when the leg  1  to which the leg brace  50  is attached becomes a stance state, to guide the center of gravity of the user toward the inner side, and thereby to alleviate a pain in the knee joint  3  caused by knee osteoarthritis when the leg  1  is an X-shaped bowleg. 
     Third Embodiment 
     Next, a third embodiment will be described with reference to  FIG. 7 . Note that the same symbols as those used in the above-described first embodiment are used for structures, components, and parts corresponding to those in the above-described first embodiment. Descriptions that are already given in the above-described first embodiment are omitted. 
       FIG. 7  shows a leg brace  70  which is attached to a leg  1  of a user when it is used. The leg brace  70  is typically used while being attached to one of the two legs  1  of the user in which the user suffers from knee osteoarthritis. However, one leg brace  70  may be attached to each of both legs  1 . In this embodiment, the leg brace  70  is attached only to the left leg  1 L of the user as shown in  FIG. 7 . 
     The leg brace  70  is attached to the leg  1  of the user and, by doing so, reduces a pain in the knee joint  3  of the leg  1 . 
     The leg brace  70  includes a thigh link  71 , a lower-leg link  72 , and extension force generation means  73 . 
     The thigh link  71  is a link that is attached to the thigh  4  of the leg  1 , and extends along the longitudinal direction of the thigh  4 . 
     The lower-leg link  72  is a link that is attached to a lower leg  5  of the leg  1 , and extends along the longitudinal direction of the lower leg  5 . 
     The lower-leg link  72  is connected to the thigh link  71  so as to be rotatable with respect thereto in the pitch direction. That is, the leg brace  70  includes a connection part  74  that rotatably connects the thigh link  71  with the lower-leg link  72 . 
     The thigh link  71  and the lower-leg link  72  form a link unit  75 . The link unit  75  is composed of the thigh link  71  and the lower-leg link  72  which is rotatable with respect to the thigh link  71 . 
     The thigh link  71  is fixed to the thigh  4  by thigh fixing bands  71   a  and  71   b.    
     The lower-leg link  72  is fixed to the lower leg  5  by lower-leg fixing bands  72   a  and  72   b.    
     The extension force generation means  73  generates an extension force between the thigh link  71  and the lower-leg link  72  in a direction in which the knee joint  3  of the leg  1  extends. As the extension force generation means  73 , it is possible to use, for example, either one of a spring or a damper that is connected to the thigh link  71  at one end above the connection part  74  and also connected to the lower-leg link  72  at the other end below the connection part  74 . As the extension force generation means  73 , it is also possible to use one that includes both a spring and a damper so that it exhibits the characteristics of the spring and the damper at the same time. 
     When a spring is used as the extension force generation means  73 , the spring may be configured so that its spring constant is adjustable. A typical example of the spring is a compression coil spring. 
     When a damper is used as the extension force generation means  73 , the damper may be configured so that its damping coefficient is adjustable. 
     Further, as shown in  FIG. 7 , the link unit  75  is disposed only on one of the inner side and the outer side of the leg  1 . According to the above-described configuration, it is possible, when the leg  1  to which the leg brace  70  is attached becomes a stance state, to guide the center of gravity of the user toward the side opposite to the side on which the link unit  75  is disposed, and thereby to alleviate a pain in the knee joint  3  caused by knee osteoarthritis. 
     Specifically, the link unit  75  is disposed on the inner side of the leg  1 . According to the above-described configuration, it is possible, when the leg  1  to which the leg brace  70  is attached becomes a stance state, to guide the center of gravity of the user toward the outer side, and thereby to alleviate a pain in the knee joint  3  caused by knee osteoarthritis when the leg  1  is an O-shaped bowleg. 
     Fourth Embodiment 
     Next, a fourth embodiment will be described with reference to  FIG. 8 . Note that the same symbols as those used in the above-described first embodiment are used for structures, components, and parts corresponding to those in the above-described first embodiment. Descriptions that are already given in the above-described first embodiment are omitted. 
       FIG. 8  shows a leg brace  80  which is attached to a leg  1  of a user when it is used. The leg brace  80  is typically used while being attached to one of the two legs  1  of the user in which the user suffers from knee osteoarthritis. However, one leg brace  80  may be attached to each of both legs  1 . In this embodiment, the leg brace  80  is attached only to the left leg  1 L of the user as shown in  FIG. 8 . 
     The leg brace  80  is attached to the leg  1  of the user and, by doing so, reduces a pain in the knee joint  3  of the leg  1 . 
     The leg brace  80  includes a thigh link  81 , a lower-leg link  82 , and extension force generation means  83 . 
     The thigh link  81  is a link that is attached to the thigh  4  of the leg  1 , and extends along the longitudinal direction of the thigh  4 . 
     The lower-leg link  82  is a link that is attached to a lower leg  5  of the leg  1 , and extends along the longitudinal direction of the lower leg  5 . 
     The lower-leg link  82  is connected to the thigh link  81  so as to be rotatable with respect thereto in the pitch direction. That is, the leg brace  80  includes a connection part  84  that rotatably connects the thigh link  81  with the lower-leg link  82 . 
     The thigh link  81  and the lower-leg link  82  form a link unit  85 . The link unit  85  is composed of the thigh link  81  and the lower-leg link  82  which is rotatable with respect to the thigh link  81 . 
     The thigh link  81  is fixed to the thigh  4  by thigh fixing bands  81   a  and  81   b.    
     The lower-leg link  82  is fixed to the lower leg  5  by lower-leg fixing bands  82   a  and  82   b.    
     The extension force generation means  83  generates an extension force between the thigh link  81  and the lower-leg link  82  in a direction in which the knee joint  3  of the leg  1  extends. As the extension force generation means  83 , it is possible to use, for example, either one of a spring or a damper that is connected to the thigh link  81  at one end above the connection part  84  and also connected to the lower-leg link  82  at the other end below the connection part  84 . As the extension force generation means  83 , it is also possible to use one that includes both a spring and a damper so that it exhibits the characteristics of the spring and the damper at the same time. 
     When a spring is used as the extension force generation means  83 , the spring may be configured so that its spring constant is adjustable. A typical example of the spring is a compression coil spring. 
     When a damper is used as the extension force generation means  83 , the damper may be configured so that its damping coefficient is adjustable. 
     Further, as shown in  FIG. 8 , the link unit  85  is disposed only on one of the inner side and the outer side of the leg  1 . According to the above-described configuration, it is possible, when the leg  1  to which the leg brace  80  is attached becomes a stance state, to guide the center of gravity of the user toward the side opposite to the side on which the link unit  85  is disposed, and thereby to alleviate a pain in the knee joint  3  caused by knee osteoarthritis. 
     Specifically, the link unit  85  is disposed on the outer side of the leg  1 . According to the above-described configuration, it is possible, when the leg  1  to which the leg brace  80  is attached becomes a stance state, to guide the center of gravity of the user toward the inner side, and thereby to alleviate a pain in the knee joint  3  caused by knee osteoarthritis when the leg  1  is an X-shaped bowleg. 
     Fifth Embodiment 
     Next, a fifth embodiment will be described with reference to  FIG. 9 . Note that the same symbols as those used in the above-described first embodiment are used for structures, components, and parts corresponding to those in the above-described first embodiment. Descriptions that are already given in the above-described first embodiment are omitted. 
       FIG. 9  shows a leg brace unit  90  which is attached to a pair of legs  1  of a user when it is used. The leg brace unit  90  includes a leg brace  90 L for a left leg  1 L and a leg brace  90 R for a right leg  1 R. 
     The leg brace unit  90  is attached to both legs  1 L and  1 R of the user and, by doing so, reduces a pain(s) in the knee joint(s)  3  of the leg(s)  1 . 
     The leg brace  90 L includes a thigh link  91 L, a lower-leg link  92 L, and extension force generation means  93 L. 
     The thigh link  91 L is a link that is attached to the thigh  4  of the left leg  1 L, and extends along the longitudinal direction of the thigh  4 . 
     The lower-leg link  92 L is a link that is attached to the lower leg  5  of the left leg  1 L, and extends along the longitudinal direction of the lower leg  5 . 
     The lower-leg link  92 L is connected to the thigh link  91 L so as to be rotatable with respect thereto in the pitch direction. That is, the leg brace  90 L includes a connection part  94 L that rotatably connects the thigh link  91 L with the lower-leg link  92 L. 
     The thigh link  91 L and the lower-leg link  92 L form a link unit  95 L. The link unit  95 L is composed of the thigh link  91 L and the lower-leg link  91 L which is rotatable with respect to the thigh link  92 L. 
     The thigh link  91 L is fixed to the thigh  4  by thigh fixing bands  91 La and  91 Lb. 
     The lower-leg link  92 L is fixed to the lower leg  5  by lower-leg fixing bands  92 La and  92 Lb. 
     The extension force generation means  93 L generates an extension force between the thigh link  91 L and the lower-leg link  92 L in a direction in which the knee joint  3  of the left leg  1 L extends. As the extension force generation means  93 L, it is possible to use, for example, either one of a spring or a damper that is connected to the thigh link  91 L at one end above the connection part  94 L and also connected to the lower-leg link  92 L at the other end below the connection part  94 L. As the extension force generation means  93 L, it is also possible to use one that includes both a spring and a damper so that it exhibits the characteristics of the spring and the damper at the same time. 
     When a spring is used as the extension force generation means  93 L, the spring may be configured so that its spring constant is adjustable. A typical example of the spring is a compression coil spring. 
     When a damper is used as the extension force generation means  93 L, the damper may be configured so that its damping coefficient is adjustable. 
     Further, as shown in  FIG. 9 , the link unit  95 L is disposed only on one of the inner side and the outer side of the left leg  1 L. In this embodiment, the link unit  95 L is disposed on the inner side of the left leg  1 L. Alternatively, the link unit  95 L may be disposed on the outer side of the left leg  1 L. 
     Similarly, the leg brace  90 R includes a thigh link  91 R, a lower-leg link  92 R, and extension force generation means  93 R. 
     The thigh link  91 R is a link that is attached to the thigh  4  of the right leg  1 R, and extends along the longitudinal direction of the thigh  4 . 
     The lower-leg link  92 R is a link that is attached to the lower leg  5  of the left leg  1 L, and extends along the longitudinal direction of the lower leg  5 . 
     The lower-leg link  92 R is connected to the thigh link  91 R so as to be rotatable with respect thereto in the pitch direction. That is, the leg brace  90 R includes a connection part  94 R that rotatably connects the thigh link  91 R with the lower-leg link  92 R. 
     The thigh link  91 R and the lower-leg link  92 R form a link unit  95 R. The link unit  95 R is composed of the thigh link  91 R and the lower-leg link  91 R which is rotatable with respect to the thigh link  92 R. 
     The thigh link  91 R is fixed to the thigh  4  by thigh fixing bands  91 Ra and  91 Rb. 
     The lower-leg link  92 R is fixed to the lower leg  5  by lower-leg fixing bands  92 Ra and  92 Rb. 
     The extension force generation means  93 R generates an extension force between the thigh link  91 R and the lower-leg link  92 R in a direction in which the knee joint  3  of the right leg  1 R extends. As the extension force generation means  93 R, it is possible to use, for example, either one of a spring or a damper that is connected to the thigh link  91 R at one end above the connection part  94 R and also connected to the lower-leg link  92 R at the other end below the connection part  94 R. As the extension force generation means  93 R, it is also possible to use one that includes both a spring and a damper so that it exhibits the characteristics of the spring and the damper at the same time. 
     When a spring is used as the extension force generation means  93 R, the spring may be configured so that its spring constant is adjustable. A typical example of the spring is a compression coil spring. 
     When a damper is used as the extension force generation means  93 R, the damper may be configured so that its damping coefficient is adjustable. 
     Further, as shown in  FIG. 9 , the link unit  95 R is disposed only on one of the inner side and the outer side of the right leg  1 R. In this embodiment, the link unit  95 R is disposed on the inner side of the right leg  1 R. Alternatively, the link unit  95 R may be disposed on the outer side of the right leg  1 R. 
     Further, the extension force of the extension force generation means  93 L of the leg brace  90 L is stronger than or weaker than that of the extension force generation means  93 R of the leg brace  90 R. According to the above-described configuration, it is possible, when a user walks, to actively guide the center of gravity of the user toward the side on which the extension force is weaker, and thereby to alleviate a pain in the knee joint  3  caused by knee osteoarthritis. 
     Specifically, in the case where the extension force of the extension force generation means  93 L of the leg brace  90 L is stronger than that of the extension force generation means  93 R of the leg brace  90 R, the center of gravity of the user is actively guided to the side of the right leg  1 R when the user walks. Therefore, when the right leg  1 R is an O-shaped bowleg, a pain in the knee joint  3  of the right leg  1 R can be alleviated. Further, when the left leg  1 L is an X-shaped bowleg, a pain in the knee joint  3  of the left leg  1 L can be alleviated. 
     Conversely, in the case where the extension force of the extension force generation means  93 L of the leg brace  90 L is weaker than that of the extension force generation means  93 R of the leg brace  90 R, the center of gravity of the user is actively guided to the side of the left leg  1 L when the user walks. Therefore, when the right leg  1 R is an X-shaped bowleg, a pain in the knee joint  3  of the right leg  1 R can be alleviated. Further, when the left leg  1 L is an O-shaped bowleg, a pain in the knee joint  3  of the left leg  1 L can be alleviated. 
     Sixth Embodiment 
     A sixth embodiment will be described hereinafter with reference to  FIG. 10 . Note that the same symbols as those used in the above-described first embodiment are used for structures, components, and parts corresponding to those in the above-described first embodiment. Descriptions that are already given in the above-described first embodiment are omitted. 
       FIG. 10  shows a lower-limb brace  101  attached to a lower limb  100  of a user. The lower limb  100  includes a leg  102  and a foot  103 . In this embodiment, the lower-limb brace  101  is attached to the foot  103 . Alternatively, the lower-limb brace  101  may be attached to the leg  102 , or to the leg  102  and the foot  103  in such a manner that the lower-limb brace  101  straddles the leg  102  and the foot  103 . 
     The lower-limb brace  101  includes a brace main body  105 , a load removal detection unit  106 , force-applying means  107 , and a control unit  108 . 
     The brace main body  105  includes a sole part  105   a  disposed on the sole of the foot  103  of the user, and an instep part  105   b  disposed on the instep side of the foot  103 . The brace main body  105  is attached to the foot  103  of the user by sandwiching the foot  103  between the sole part  105   a  and the instep part  105   b . However, the shape of the brace main body  105  is not limited to the above-described example. 
     The load removal detection unit  106  detects that a load exerted on the lower limb  100  is removed. The load removal detection unit  106  is typically a pressure sensor, and is disposed in the sole part  105   a . Alternatively, the load removal detection unit  106  may adopt other configurations by which it can detect that a load exerted on the lower limb  100  is removed. For example, the load removal detection unit  106  may use a contact sensor or the like. It can be considered that the timing at which a load on the lower limb  100  is removed is substantially simultaneous with the timing at which the state of the lower limb  100  changes from a stance state to a swing state. The load removal detection unit  106  outputs the result of the detection to the control unit  108 . 
     The force-applying means  107  is capable of applying a force to the brace main body  105  in a direction in which the brace main body  105  recedes from the ground surface, and typically includes a solenoid coil and a rod that moves forward and backward according to the energization of the solenoid coil. For example, when the solenoid coil is energized, the rod is driven to move toward the ground surface, so that the force-applying means  107  applies a force to the brace main body  105  in a direction in which the brace main body  105  recedes from the ground surface. 
     The control unit  108  controls the force-applying means  107  so that when the load on the lower limb  100  is removed, the force-applying means  107  applies a force to the brace main body  105  in the direction in which the brace main body  105  recedes from the ground surface. 
     The control unit  108  includes a CPU (Central Processing Unit) that serves as a central processing unit, a readable/writable RAM (Random Access Memory), and a read-only ROM (Read Only Memory). Further, when the CPU loads and executes a control program stored in the ROM, the control program causes hardware such as the CPU to function as the control unit  108 . 
     According to the above-described configuration, it is possible, when a user walks, to guide the center of gravity of the user toward the lower limb  110  opposite to the lower limb  100  to which the lower-limb brace  101  is attached at the timing when the state of the lower limb  100  changes from a stance state to a swing state. Therefore, it is possible to alleviate a pain in the knee joint  3  caused by knee osteoarthritis of the lower limb  110  when the lower limb  110  opposite to the lower limb  100  to which the lower-limb brace  101  is attached is an O-shaped bowleg. 
     The stance state of the leg is a state where the corresponding foot is in contact with the floor, while the swing state of the leg is a state where the corresponding foot is not in contact with the floor. 
     The program can be stored and provided to a computer using any type of non-transitory computer readable media. Non-transitory computer readable media include any type of tangible storage media. Examples of non-transitory computer readable media include magnetic storage media (such as floppy disks, magnetic tapes, hard disk drives, etc.), optical magnetic storage media (e.g. magneto-optical disks), CD-ROM (compact disc read only memory), CD-R (compact disc recordable), CD-R/W (compact disc rewritable), and semiconductor memories (such as mask ROM, PROM (programmable ROM), EPROM (erasable PROM), flash ROM, RAM (random access memory), etc.). The program may be provided to a computer using any type of transitory computer readable media. Examples of transitory computer readable media include electric signals, optical signals, and electromagnetic waves. Transitory computer readable media can provide the program to a computer via a wired communication line (e.g. electric wires, and optical fibers) or a wireless communication line. 
     From the disclosure thus described, it will be obvious that the embodiments of the disclosure may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure, and all such modifications as would be obvious to one skilled in the art are intended for inclusion within the scope of the following claims.