Patent Publication Number: US-7721467-B2

Title: Shoe insole with improved support and motion control

Description:
The present application claims priority to U.S. Provisional application No. 60/732,799 for SHOE INSOLE, filed Nov. 2, 2005, which application is incorporated herein in its entirety by this reference. 
    
    
     The present invention relates in general to an improved shoe insole and more particularly to an insole for women adapted to provide improved cushioning, support, and motion control. 
     BACKGROUND OF THE INVENTION 
     The human foot is a very complex biological mechanism. While standing, the feet carry a persons entire weight. While walking the load on a foot at heel strike is typically about one and a half times a person&#39;s body weight. When running or carrying extra weight the loads on the foot may exceed three times the body weight. The many bones, muscles, ligaments, and tendons of the foot function to absorb and dissipate the forces of impact, carry the weight of the body and other loads, and provide forces for propulsion. Properly designed shoe insoles can assist the foot in performing these functions and protect the foot from injury. 
     To be practical for distribution to the general public, an insole must be able to provide benefit to the user population without requiring individualized adjustment and fitting. Insoles can be optimized to address the needs of different portions of the user population. For example, insoles can be designed to accommodate the biomechanical differences between men and women. 
     Biomechanically men and women are very similar in most respects. They share basically the same human design, with the same number of bones, muscles, ligaments, and a torso that supports two upper and lower limbs. However, there are some biomechanical differences. The most distinguishing anatomical feature between men and women is the pelvis. To facilitate child birth, the pelvis of a woman is typically broader and rounder than that of a man. As a result, in women the thigh bone or femur approaches the knee at a greater angle than in men. This angle, called the quadriceps angle or Q-angle, is, on average, about 18 degrees in women compared to about 13 degrees in men. This angulation places greater stress at the knee joint of most women, making them more vulnerable to misalignment injuries, such as anterior cruciate ligament tears at the knee, 4 th  and 5 th  metatarsal fractures, peroneal tendonitis, iliotibial band syndrome, and other injuries. Because women also typically have narrower heels and lighter bone structure across the tri-planar axis of the foot, they are more susceptible to over use injuries and compensatory injuries when trying to reduce stress along the medial aspect of the knee joint 
     Women compensate for a greater Q-angle by moving their center of mass laterally to the outside to place the leg in a straighter alignment over the foot. Women also tend to pronate more than men because their foot strikes the ground in a more supinated position on the outside of their feet during foot strike. 
     In view of the foregoing, it would be desirable to provide an over-the-counter insole that provides cushioning adapted to the biomechanics of women. 
     It would also be desirable to provide an insole that provides pronation control adapted to the unique biomechanics of women. 
     SUMMARY OF THE INVENTION 
     The above, and other objects and advantages of the present are provided by an insole that provides both motion control and cushioning. The insole includes a system of interacting components that cooperate to achieve a desired combination of foot cushioning and motion control. The components include a base, a lateral and medial cradle, a heel plug, and a number of elastomeric pads. The characteristics of these components, their size and shape, and their position are selected to provide a desired blend of cushioning and control, and more specifically to achieve a desired biomechanical function. 
     In accordance with principles of the present invention, a cushioning base is combined with firmer pads along the medial side, lateral side, and rear of the foot to form a cradle to support the foot while providing cushioning, stability, and control. Additional elastomeric pads under the heel and forefoot provide additional cushioning. By altering the size, shape, and material properties of the pods insoles may be designed to address issues related to foot motion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above, and other objects and advantages of the present invention will be understood upon consideration of the following detailed description taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which: 
         FIG. 1  is a exploded perspective view of an illustrative embodiment of an insole in accordance with the principles of the present invention; 
         FIGS. 2 to 4  are, respectively, plantar (bottom), medial (inside), and lateral views of the insole of  FIG. 1 ; 
         FIGS. 5 to 8  are transverse cross sectional views of the insole of  FIG. 2 ; and 
         FIG. 9  is a longitudinal cross sectional view of the insole of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     In reference to  FIGS. 1 to 9 , an insole constructed in accordance with the principles of the present invention is disclosed. The insole is for use inside a user&#39;s shoe and has a shape which will generally conform to the inside of a shoe. As shown in the exploded view of  FIG. 1 , insole  20  is a composite structure including base  22 , cushioning pad  24 , lateral border  26 , medial border  28 , heel plug  30 , forefoot pad  32 , and top sheet  34 . 
     As shown in  FIG. 1 , base  22  generally has the shape of a partial insole extending from behind the heel to the area of the forefoot. Base  22  is made of a foam or other durable material having suitable cushioning and support properties. For example, base  22  is preferably made of a polyurethane foam of about 3 to 12 mm thick and having a durometer of about 49 to 53 Asker C. 
     Base  22  has a raised edge that wraps around the heel and extends partially along the sides of the foot such that the insole conforms to the natural shape of the foot. As best seen in  FIGS. 5-9 , the height of the raised edge is generally higher, and the base material is thicker, on the medial side of the foot and is lower on the lateral side. Base  22  includes thicker portions in the shape of pods generally along a centerline of the foot. Base  22  further includes indented areas or regions designed to accept various pads and plugs as discussed below. Preferably, the base extends from the heel through the mid-foot area and defines a first recess in the bottom of the base and extending along a lateral side of the base for receiving a lateral border as specified below and a second recess in the bottom of the base and extending from behind the heel along the medial side of the base through the longitudinal arch for receiving a medial border as specified below. 
     Cushioning pad  24  is disposed on the upper surface of base  22  and generally extends under the entire foot, from the heel to the toes. Cushioning pad is made of a softer cushioning material than base  22  to control and distribute the initial impact of foot strike. For example, cushioning pad  24  is preferably a neoprene foam layer about 2 to 3 mm thick and having a durometer of about 21 Asker C. 
     An upper surface of cushioning pad  24  is covered with top sheet  34 , which is preferably a non-woven fabric layer with a low coefficient of friction so as to minimize the possibility of blisters. The fabric is treated with an antibacterial agent, which in combination with a moisture barrier reduces odor causing bacteria and fungus. A series of air ports extending through insole  20  permit air circulation above and below insole  20 . 
     Lateral border  26  and medial border  28  cooperate to form a cradle that generally extends from the heel through the midtarsal joints of the foot. Lateral border  26  extends along the lateral side of the foot from beside the calcaneous to the forefoot. Medial border  28  wraps around behind a portion of the calcaneous and extends along the inside of the foot through the arch to support and cushion the inside of the foot. The lateral and medial borders are secured to the lateral and medial recesses respectively in the base. Lateral cradle  26  and medial cradle  28  are made of a firmer material than base  22 . For example, lateral cradle  26  and medial cradle  28  are preferably made of a polyurethane material having a durometer in the range of about 60 to 70 Asker C. The use of pads or cushions made of materials of differing density, or hardness, in conjunction with the shape and placement of the pads provides cushioning and control to help compensate for the increased O-angle in women. The size, shape, and placement of these pads are based on the location of various anatomical landmarks of the foot and the biomechanics of foot motion. 
     As shown in  FIGS. 5 to 9 , lateral border  26  and medial border  28  wrap up the sides and/or rear of base  22  to provide support for the foot. The sides of stability medial border  28  are preferably higher than the lateral border because of the higher loading. For example, medial cradle  28  extends upward under the medial longitudinal arch to provide longitudinal arch support. 
     Biological tissues such as tendons and ligaments are sensitive to the rate at which they are loaded, the abrupt change in load may cause injury or damage. Together, base  22 , lateral border  26 , and medial border  28  function to place the female foot in better biomechanical alignment with the leg and to balance their anatomical structure to reduce compensatory injuries. The medial arch support provided by base  22  and medial border  28  slows down the rate of pronation and improves balance for the foot. The medial border  28  also cooperates with the rear portion of the lateral border  26  to provide added rearfoot stability. The lateral border  26  extends beyond the fifth metatarsal bone with a cuboid support that functions to lock the midtarsal at midstance. 
     A forefoot pad  32  may be a third pad or component in addition to the cushioning pad  24  and base  22  lateral border  26 , medial border  28  as best illustrated in  FIG. 1 . It may be employed also with heel plug  30  and/or top sheet  34 . It is disposed on a top surface of the base and extends forward of the base. The material of the forefoot pad is preferably from about 16 to 27 Asker C. Forefoot pad  32  is positioned under the toes of the foot to provide cushioning of the toes during toe off. For example, pad  32  may comprise a 1.5 mm layer of neoprene having a durometer of about 21 Asker C. 
     The base is preferably provided with a recess adapted to receive a heel pad or plug. Preferably, the heel pad or plug is made of a material having a firmness of about 17 to 28 Asker C. The heel plug may be one the five components in addition to the cushioning pad  24  and base  22  as best illustrated in  FIG. 1  as lateral border  26 , medial border  28  forefoot pad  32  and top sheet  34 . The heel plug is preferably made of gel. Gel heel plug  30  fits into a recess in base  22  and provides additional cushioning at foot strike. Heel plug  30  preferably has a durometer of about 22 Asker C. 
     An upper surface of cushioning pad  24  is covered with top sheet  34 , which is preferably a non-woven fabric layer with a low coefficient of friction so as to minimize the possibility of blisters. The fabric is treated with an antibacterial agent, which in combination with a moisture barrier reduces odor causing bacteria and fungus. A series of air ports extend through top sheet  34 , cushioning pad  24 , and forefood pad  32  to permit air circulation above and below insole  20 . 
     While the present invention has been described in relation to preferred embodiments, the detailed description is not limiting of the invention and other modifications will be obvious to one skilled in the art. For example, in the illustrative embodiment of the invention disclosed above the lateral and medial borders have the same firmness. However, over- or under-pronation may be addressed by using a material of different firmness. 
     The present invention has been disclosed in the context of providing an over-the-counter insole that may be made available for distribution to the general public. However, the same principles may be used by a podiatrist or other medical professional to design or create an insole to address the needs of a specific patient. 
     Thus, an improved insole has been disclosed. It will be readily apparent that the illustrative embodiment of an insole thus disclosed may be useful in cushioning the foot and controlling pronation. However, one will understand that the components of the insole system may be modified to achieve other ends. Thus, the description provided herein, including the presentation of specific thicknesses, materials, and properties of the insole components, is provided for purposes of illustration only and not of limitation, and that the invention is limited only be the appended claims.