Abstract:
A knee joint prosthesis assembly can include a femoral component that has a medial and a lateral condyle portion connected by a patellar track portion. The femoral component can form an opening between the medial and lateral condyles. A tibial component can have a medial portion that includes a first engagement structure and a lateral portion that includes a second engagement structure. A medial bearing can have a third engagement structure formed thereon that selectively engages the first engagement structure. A lateral bearing separately formed and independent from the medial bearing can have a fourth engagement structure formed thereon that selectively engages the second engagement structure.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 12/788,961 filed on May 27, 2010 which claims the benefit and priority of 61/181,938, filed May 28, 2009. The entire disclosure of the above applications is incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates to a knee joint prosthesis including a tibial tray component having independent and selectively attachable bearings including fixed and mobile bearings that can be secured to medial and lateral sides of the tibial tray according to the needs of a particular patient. 
     BACKGROUND 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     A knee joint prosthesis can generally comprise a femoral component and a tibial component. The femoral component and the tibial component can be designed to be surgically attached to the distal end of the femur and the proximal end of the tibia, respectively. The femoral component can further be designed to cooperate with the tibial component in simulating the articulating motion of an anatomical knee joint. In many examples, the tibial component can further include a bearing component that includes articulation surfaces on the medial and lateral side for cooperating with a medial and lateral condyle portion of the femoral component. In some examples, the bearing component can be fixed relative to the tibial component. In other examples, the bearing component can be a mobile bearing component that has at least a portion that can move relative to the tibial component during articulation of the femoral component. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     A knee joint prosthesis assembly can include a femoral component that has a medial and a lateral condyle portion connected by a patellar track portion. The femoral component can form an opening between the medial and lateral condyles. A tibial component can have a medial portion that includes a first engagement structure and a lateral portion that includes a second engagement structure. A medial bearing can have a third engagement structure formed thereon that selectively engages the first engagement structure. A lateral bearing separately formed and independent from the medial bearing can have a fourth engagement structure formed thereon that selectively engages the second engagement structure. 
     According to other features, one of the medial and lateral bearings can be fixed relative to the tibial component and the other of the medial and lateral bearings can be a mobile bearing component. 
     According to still other features, the mobile bearing component can include a fixed portion that has the third or fourth engagement structure that is configured to statically engage the tibial component and a mobile bearing portion that is configured to slidably advance along the opposing surface of the tibial component. The fixed portion can define a pocket that receives and confines the mobile bearing portion therewithin. The mobile bearing portion can be formed of a polymeric material and can include a metallic layer of material disposed around a perimeter thereof. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1  is an anterior perspective view of a knee prosthesis assembly according to one example of the present teachings; 
         FIG. 2  is a posterior perspective view of the knee prosthesis of  FIG. 1 ; 
         FIG. 3  is a lateral perspective view of a femoral component of the knee prosthesis of  FIG. 1 ; 
         FIG. 4  is a superior perspective view of a tibial tray of the knee prosthesis of  FIG. 1 ; 
         FIG. 5  is an inferior perspective view of the tibial tray of  FIG. 4 ; 
         FIG. 6  is a perspective view of a mobile bearing of the knee prosthesis of  FIG. 1 ; 
         FIG. 7  is a perspective view of a fixed bearing of the knee prosthesis of  FIG. 1 ; 
         FIG. 8  is a perspective view of a locking bar associated with the fixed bearing of a knee prosthesis of  FIG. 1 ; 
         FIG. 9  is a partially exploded posterior view of a knee prosthesis constructed in accordance to additional features of the present teachings; 
         FIG. 10  is a posterior perspective view of the knee prosthesis of  FIG. 9 ; 
         FIG. 11  is an anterior perspective view of a tibial tray and fixed bearing portion of the knee prosthesis of  FIG. 10 ; 
         FIG. 12  is a perspective view of a mobile bearing that slidably cooperates within a pocket formed on the fixed bearing of  FIG. 11 ; 
         FIG. 13  is an anterior perspective view of a knee prosthesis assembly according to another example of the present teachings that incorporates a mobile bearing component that is selectively attachable to a medial side of a tibial tray and a fixed bearing component that is selectively attachable to a lateral side of the tibial tray; 
         FIG. 14  is an anterior superior exploded perspective view of the knee prosthesis assembly of  FIG. 13 ; 
         FIG. 15  is an anterior inferior exploded perspective view of the knee prosthesis assembly of  FIG. 13 ; 
         FIG. 16  is a perspective view of a mobile bearing incorporating a metal sleeve according to various features; 
         FIG. 17  is an anterior perspective view of a tibial tray constructed in accordance to additional features and incorporating a pair of fixed bearings that are selectively locked to the tibial tray with a locking bar; 
         FIG. 18  is an anterior superior exploded perspective view of the tibial tray assembly of  FIG. 17 ; 
         FIG. 19  is an anterior inferior exploded perspective view of the tibial tray assembly of  FIG. 17 ; 
         FIG. 20  is an anterior perspective view of a tibial tray constructed in accordance to additional features of the present teachings; and 
         FIG. 21  is a kit having a plurality of tibial trays, medial bearings and lateral bearings according to the present teachings. 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully with reference to the accompanying drawings. 
     With initial reference to  FIGS. 1 and 2 , a knee prosthesis assembly constructed in accordance to one example of the present teachings is shown and generally identified at reference numeral  10 . The knee prosthesis assembly  10  can generally include a femoral component  12 , a tibial tray  14 , a medial floating or mobile bearing  16  and a lateral fixed bearing  18 . As will be described, the knee prosthesis assembly  10  can be used when it is desirable to retain or reconstruct an anterior cruciate ligament (ACL) and/or a posterior cruciate ligament (PCL). 
     The respective components of the knee prosthesis assembly  10  can be patient specific, such that each component can be constructed for optimal features for a given patient. For example, the bone interface margins of the femoral component  12  and tibial tray  14  can be patient specific for optimized bone coverage. In addition, the overall size, such as anterior-posterior dimensions and bone cut geometry can be determined and used for manufacturing the components of the knee prosthesis assembly  10 . Moreover, some articulation features can be determined and used as criteria for forming the components of the knee prosthesis assembly  10 . In sum, each of the components of the knee prosthesis assembly  10  can be a patient-specific implant, a semi-custom implant or an off-the-shelf or standard production implant. A custom-made implant is a patient-specific, one-of-a-kind implant specifically made for a particular patient, and consequently there is no inventory associated with such implant. Standard or off-the shelf implants are available and stocked in a number of sizes, typically six or more, and a number of configurations or types, including bilateral or unilateral implants, constrained, semi-constrained, mobile, etc. Because of the variety of sizes and configurations that are kept in stock to be accommodated by different patients, a large inventory of standard implants is created, and several molds for each type and size of implant may be used. Semi-custom implants can provide an intermediate solution between custom-made and off-the-shelf implants. Semi-custom implants reduce the size of inventory and molds required for production, while allowing some degree of patient-specific customization. Additional description of patient-specific implants and semi-custom implants and their implementations may be found in copending patent application Ser. No. 12/103,824, filed Apr. 16, 2008 and entitled: Method and Apparatus for Manufacturing an Implant, the disclosure of which is hereby incorporated by reference. 
     With additional reference to  FIG. 3 , the femoral component  12  will now be described in greater detail. The femoral component  12  can generally comprise a cruciate retaining prosthesis and includes various portions to replace or mimic the distal femur. The femoral component  12  can include a medial condyle portion  20  and a lateral condyle portion  22 . The condyle portions  20  and  22  can replace the medial and lateral condyles of a distal femur. The medial and lateral condyle portions  20  and  22  can interconnect and be formed as a single piece with a patellar track portion  26 . The patellar track portion  26  can allow for articulation of a patella, either natural or prosthetic patella, once the femoral component  12  is implanted onto the distal femur. The medial and lateral condyle portions  20  and  22  and the patellar track portion  26  can generally define an exterior portion of the femoral component  12 . The femoral component  12  can define an opening or passage  30  between the medial and lateral condyle portions  20  and  22 . As can be appreciated, the passage  30  can accommodate, and provide clearance for a host ACL and/or PCL or a reconstructed ACL and/or PCL. The medial condyle portion  20  can include a spherical contact surface that is convex in an anterior/posterior direction and a medial/lateral direction. 
     The femoral component  12  can include a bone contacting or inferior surface  34  ( FIG. 2 ). The inferior surface  34  can include an anterior surface  36  that can be substantially flat and formed generally parallel to a pair of posterior surfaces  38   a  and  38   b . A pair of intermediate surfaces  40   a  and  40   b  are provided generally at an intermediate portion of the inferior surface  34 . A pair of angled anterior transition surfaces  42   a  and  42   b  generally connect the anterior surface  36  with the intermediate surfaces  40   a  and  40   b . Similarly, a pair of angled posterior transition surfaces  44   a  and  44   b  are provided between the respective posterior surfaces  38   a  and  38   b  and the intermediate surfaces  40   a  and  40   b . In one example, a threaded boss  50   a  and  50   b  can be provided on each of the intermediate surfaces  40   a  and  40   b , respectively. Similarly, a threaded boss  52   a  and  52   b  can be provided on the posterior surfaces  38   a  and  38   b , respectively. The bosses  50   a ,  50   b ,  52   a  and  52   b  can be optionally used to threadably couple with various augments (not specifically shown) as necessary. The femoral component  12  can be formed as a unitary structure and cast of a biocompatible high strength alloy, such as cobalt-chromium-molybdenum alloy or similar suitable material. All surfaces, which do not contact the femur, can be highly polished to provide smooth articulating bearing surfaces. The interior surface  34  of the femoral component  12  can be roughened or uneven or include porous material to allow bone ingrowth or attachment with bone cement. Other features of the femoral component  10  can include those associated with the Oxford® Partial Knee marketed by Biomet, Inc. 
     With reference now to  FIGS. 1 ,  2 ,  4  and  5 , the tibial tray  14  will now be described in greater detail. The tibial tray  14  can include a generally U-shaped body having a medial portion  60  and a lateral portion  62 . A slot  64  can be formed in the tibial tray  14  generally between the medial and lateral portion  60  and  62 . As with the passage  30  of the femoral component, the slot  64  of the tibial tray  14  can accommodate and provide a clearance for a host ACL and/or PCL or a reconstructed ACL and/or PCL. During implantation, the tibial tray  14  can be advanced posteriorly, such that the slot  64  can accommodate a host ACL and/or PCL. In instances where a reconstructed ACL and/or PCL is used, a tray (and bearing) having a passage can be utilized. One suitable configuration is further described in commonly owned in U.S. Pat. No. 7,255,715; issued Aug. 14, 2007 and is hereby incorporated by reference. The tibial tray  14  can include an inferior bone engaging side  66  ( FIG. 5 ) and a superior bearing engaging side  68  ( FIG. 4 ). The medial portion  60  of the superior bearing engaging side  68  can include a highly polished tibial bearing surface  70 . A rail  72  can extend in a generally anterior/posterior direction adjacent to the highly polished tibial bearing surface  70 . The lateral portion  62  can include engaging structure  78  provided on the superior bearing engaging side  68 . The engaging structure  78  can include a pair of posts  80  and  82  integrally formed at an anterior edge thereof. A retaining rail  84  can extend superiorly from a posterior edge of the lateral portion  62 . The posts  80  and  82  can both have an anterior groove  86  and a posterior groove  88 , respectively. The retaining rail  84  can have a transverse groove  90  formed on an inwardly facing surface. The tibial tray  14  can be generally manufactured of cobalt-chromium-molybdenum alloy or other suitable biocompatible material. A pair of fins  94  can extend from the inferior bone engaging side  66 . While fins  94  are shown operatively associated with the tibial tray  14 , other structures suitable for engaging a proximal tibia can include pegs, posts or porous material can additionally or alternatively be provided on the inferior bone engaging side  66 . 
     With reference to  FIGS. 1 ,  2  and  6 , the medial floating bearing  16  will now be described in greater detail. The medial floating bearing  16  has a substantially planar inferior bearing surface  100  which slidably moves and articulates relative to the highly polished tibial bearing surface  70 . The medial floating bearing  16  further includes a first bearing surface  102 . The first bearing surface  102  articulates with the medial condyle portion  20  of the femoral component  12 . The medial floating bearing  16  can be formed from a surgical grade, low friction, and low wearing plastic, such as ultra high molecular weight polyethylene (UHMWPE) or other suitable material. 
     With reference to  FIGS. 1 ,  2  and  7 , the lateral fixed bearing  18  can include engaging structure  106  formed on an inferior surface for coupling with the engaging structure  78  provided on the lateral portion  62  of the tibial tray  14 . The engaging structure  106  can generally include a posteriorly extending lip  110  and an anterior groove  112 . A locking bar  114  ( FIG. 8 ) can be slidably inserted through the anterior groove  112  to interlock between the respective grooves  86  to capture the lateral fixed bearing  18  to the lateral portion  62  of the tibial tray  14 . The posteriorly extending lip  110  can be nestingly received by the retaining rail  84 . The lateral fixed bearing  18  can include a second bearing surface  120 . The second bearing surface  120  can articulate with the lateral condyle portion  22  of the femoral component  12 . The lateral fixed bearing  18  can be formed from a surgical grade, low friction and low wearing plastic, such as UHMWPE or other suitable material. 
     During use, the medial and lateral condyle portions  20  and  22  of the femoral component  12  can articulate on the first and second bearing surfaces  102  and  120  of the respective medial floating bearing  16  and lateral fixed bearing  18 . As can be appreciated, the lateral fixed bearing  18  is static relative to the tibial tray  14  during articulation of the femoral component  12 . The medial floating bearing  16  is free to slide along the highly polished tibial bearing surface  70  of the medial portion  60  of the tibial tray  14 . The medial floating bearing  16  is bound on an inboard side by the rail  72 . 
     While the embodiment shown in the figures includes a floating bearing provided on a medial side and a fixed bearing provided on a lateral side, the location of these bearings can be swapped. Similarly, both of the medial and lateral sides can be formed with floating bearings or fixed bearings. Turning now to  FIGS. 9-11 , a knee prosthesis assembly constructed in accordance to additional features of the present teachings is shown and generally identified at reference numeral  210 . The knee prosthesis assembly  210  can generally include a femoral component  212 , a tibial tray  214 , a medial side having a mobile bearing component  216  and a lateral side having a fixed bearing  220 . The mobile bearing component has a fixed portion  217  and a mobile bearing portion  218 . The femoral component  212  can be constructed similar to the femoral component  12  described below. The fixed bearing  220  can be constructed similar to the lateral fixed bearing  18  described above. The mobile bearing component  216  can provide articulation that is fully conforming with the femoral component  212 . The mobile bearing portion  218  can be captured around its perimeter by a pocket  222  formed by the fixed portion  217 . In this way, the mobile bearing portion  218  can have a reduced likelihood of becoming dislocated relative to the fixed portion  217 . While the mobile bearing component  216  is shown generally associated with the lateral side of the tibial tray  214 , such a configuration can be additionally or alternatively provided on the medial portion of the tibial tray  214 . In one example, the mobile bearing portion  218  can be formed by polyethylene or polyetheretherketone (PEEK). As shown in  FIG. 11 , the fixed portion  217  can have a pair of channels  226  formed thereon for guiding tabs  230  provided on the mobile bearing portion  218  ( FIG. 12 ). It will be appreciated that while the mobile bearing component  216  has been described and shown incorporated on a medial portion of the tibial tray  214 , it can additionally or alternatively be incorporated on a lateral portion of the tibial tray  214 . Likewise, while the fixed bearing  220  has been described and shown incorporated on a lateral portion of the tibial tray  214 , it can additionally or alternatively be incorporated on a medial portion of the tibial tray  214 . 
     With reference now to  FIGS. 13-16 , a knee prosthesis assembly  310  constructed in accordance to additional features of the present teachings will be described. As with the other knee prosthesis assemblies disclosed herein, the knee prosthesis assembly  310  can be patient specific, such that each component can be constructed for optimal features for a given patient. In this regard, the knee prosthesis assembly  310  can generally include the femoral component  12 , a tibial tray  314 , a mobile bearing component  316  and a fixed bearing component  318 . As shown, the mobile bearing component  316  is selectively secured to a medial portion  320  of the tibial tray  314  and a fixed bearing component  318  selectively secured to a lateral portion  322  of the tibial tray  314  for a left knee. However, it will be appreciated by those skilled in the art that a mobile bearing component  316  can be provided for both the medial portion  320  and the lateral portion  322  of the tibial tray  314 . Similarly, a fixed bearing component  318  can be provided for both of the medial portion  320  and the lateral portion  322  of the tibial tray  314 . Likewise, the fixed bearing component  318  can alternatively be provided only on the medial portion  320 , while a medial bearing component  316  can be provided only on a lateral portion  322  of the tibial tray  314 . In sum, any combination of mobile and fixed bearing components can be available and selectively secured to either of the medial or lateral portions  320  and  322  of the tibial tray  314 . 
     The femoral component  12  can be generally formed similar to the femoral component  12  described in detail above. Again, the medial condyle portion  20  can have a spherical, convex articulation surface that can cooperate with the mobile bearing components  316  as will be described herein. It is appreciated that a similar spherical, convex articulation surface can be provided on the lateral condyle portion  22  in the event that a mobile bearing component is desired on the lateral portion  322  of the tibial tray  314 . 
     The mobile bearing component  316  can generally include a fixed portion  330  and a mobile bearing portion  332  ( FIG. 14 ). The fixed portion  330  can generally include a pocket  334  defined within a surrounding wall  336 . A superior surface  338  can be contoured to cooperate with the profile of the medial condyle portion  20  of the femoral component  12 . An inferior surface  340  ( FIG. 15 ) can have a channel  342  that tapers generally anteriorly for locking with a portion of the tibial tray  314  as further discussed herein. The pocket  334  extends through the fixed portion  330  from the superior surface  338  to the inferior surface  340  to permit an inferior surface  354  of the mobile bearing portion  332  to abut the tibial tray  314 . A rail  346  can be formed into the surrounding wall  336 . A groove  348  can be formed around a posterior edge of the fixed portion  330 . The fixed portion  330  can have an inner wall  349  that cooperates with the U-shaped profile of the tibial tray  314  to accommodate a host or reconstructed ACL. 
     The mobile bearing portion  332  can have an outer perimeter surface  350  that substantially matches a profile of the surrounding wall  336 , however, is reduced in size so as to be stepped inwardly relative to the surrounding wall  336  (see also  FIG. 9 ) to allow movement within the surrounding wall  336 . Tabs  352  can extend in generally the medial and lateral directions from the inferior surface  354  of the mobile bearing portion  332 . A superior articulating surface  358  can substantially conform to the profile of the medial condyle portion  20  of the femoral component  12 . The fixed portion  330  and the mobile bearing portion  332  can be formed of UHMWPE or PEEK. According to additional features, a mobile bearing portion  332 ′ ( FIG. 16 ) can have a metal layer or band  359  disposed around a perimeter. The metal layer  359  can preclude polymer-polymer contact between the perimeter of the mobile bearing portion  332 ′ and the surrounding wall  336  of the fixed portion  330  to inhibit wear. As shown in  FIG. 16 , similar features are identified with common reference numerals having a “prime” suffix. 
     The fixed bearing component  318  can generally include a superior surface  360  that substantially conforms to and provides a surface contact with the profile of the lateral condyle portion  22  of the femoral component  12 . A channel  362  can be formed along an anterior inferior surface  364  and that generally tapers anteriorly. A groove  368  can be formed around a posterior edge of the fixed bearing component  318 . The fixed bearing component  318  can have an inner wall  369  that cooperates with the U-shaped profile of the tibial tray  314  to accommodate a host or reconstructed ACL. 
     The tibial tray  314  can generally include a locating tab  370  formed on an anterior edge of the medial portion  320  and a locating tab  372  formed on an anterior edge of the lateral portion  322 . A slot  374  can be defined through the tibial tray  314  between the medial and lateral portions  320  and  322 . The slot  374  can be configured to accommodate and provide clearance for a host ACL and/or PCL or a reconstructed ACL and/or PCL. A retaining rail  375  can be formed around a posterior edge of the medial portion  320 . The retaining rail  375  can include a lip  376  and a groove  378 . A retaining rail  380  can be formed around a posterior edge of the lateral portion  322  of the tibial tray  314 . The retaining rail  380  can generally include a lip  382  and a groove  384 . An inferior surface  386  of the tibial tray  314  can be generally smooth, but may also incorporate a series of round grooved pegs. The inferior surface  386  can be configured to be cemented or press-fit onto the proximal tibia. The tibial tray  314  can be generally manufactured of cobalt-chromium-molybdenum alloy or other suitable biocompatible materials. 
     Attaching the mobile bearing component  316  to the medial portion  320  of the tibial tray  314  will now be described according to one example. At the outset, the surgeon can select a given medial bearing component  316  from a plurality of medial bearing components (see also kit  600 ,  FIG. 21 ) that satisfies the desired characteristics for a given patient, such as height, articulation, etc. The mobile bearing portion  332  can be initially advanced into the pocket  334  superiorly, such that the tabs  352  can generally locate against the rail  346  formed on the fixed portion  330 . Concurrently or subsequently, the fixed portion  330  can be located onto the medial portion  320  of the tibial tray  314  along with the mobile bearing portion  332  in an assembly. Next, a surgeon can slidably advance the mobile bearing component  316  in a directly generally posteriorly such that the channel  342  is progressively advanced around the locating tab  370  and the groove  348  of the fixed portion  330  is located under the lip  376  of the retaining rail  375  on the tibial tray  314 . It will be appreciated that at this point, the fixed portion  330  remains static relative to the medial portion  320  of the tibial tray  314  while the mobile bearing portion  332  is free to slidably advance around the medial portion  320  of the tibial tray  314  within the confines of the surrounding wall  336  of the pocket  334 . It can be appreciated that articulation of the medial condyle portion  20  of the femoral component on the superior articulating surface  358  of the mobile bearing portion  332  can influence the mobile bearing portion  332  to rotate and/or slidably advance such as in an anterior/posterior direction along the medial portion  320  around the pocket  334 . 
     Connection of the fixed bearing component  318  to the lateral portion  322  of the tibial tray  314  is similarly carried out. Initially, the inferior surface  364  of the fixed bearing component  318  is located onto the lateral portion  322  of the tibial tray  314 . Next, the fixed bearing component  318  is slidably advanced posteriorly, such that the channel  362  slidably accommodates the locating tab  372  while the groove  368  locates under the lip  380 . The fixed bearing component  318  is adapted to be statically secured relative to the lateral portion  322  of the tibial tray when assembled. 
     With reference now to  FIGS. 17-19 , a tibial tray assembly  413  constructed in accordance to additional features of the present teachings will be described. As with the other knee prosthesis assemblies disclosed herein, the tibial tray assembly  413  can be patient specific, such that each component can be constructed for optimal features for a given patient. In this regard, the tibial tray assembly  413  can include a tibial tray  414 , a first bearing component  416 , a second bearing component  418  and a locking bar  420 . As with the tibial tray  314  described above, the tibial tray  414  can be generally U-shaped and provides a slot  422  that can be configured to accommodate and provide clearance for a host ACL and/or PCL or a reconstructed ACL and/or PCL. Other examples of attaching an artificial or natural ACL and/or PCL may be found in “Knee Prosthesis Assembly with Ligament Link” Ser. Nos. 12/788,966 and 12/788,973, filed concurrently herewith. As with the other bearing components disclosed herein, the first bearing component  416  and the second bearing component  418  are both independently formed and intraoperatively selected according to the needs of a given patient. The first bearing component  416  and the second bearing component  418  are generally fixed bearing components, however, a mobile bearing component may be similarly provided for either of the medial and/or lateral sides. As will become appreciated from the following discussion, the locking bar  420  can be used to selectively and intraoperatively secure the respective first and second bearing components  416  and  418  to the tibial tray  414 . The first bearing component  416  can have a superior surface  424 , an inferior surface  426  ( FIG. 19 ) having engagement grooves  427  and an anterior channel  428 . Similarly, the second bearing component  418  can include a superior surface  430 , an inferior surface  432  ( FIG. 19 ) having engagement grooves  433  and an anterior channel  434 . 
     The tibial tray  414  can include a medial portion  436 , a lateral portion  438 , posterior engagement tabs  440 , an anterior engagement bridge  442  and anterior engagement tabs  443 . The anterior engagement bridge  442  can include a track  444  formed thereon. The anterior engagement bridge  442  can provide an increased thickness to the tibial tray  414  at the connection between the medial and lateral portion  436  and  438 , respectively to increase durability. A wall  446  can be formed on the anterior engagement bridge  442  adjacent to the track  444 . The tibial tray  414  can have inferiorly extending posts  450 . 
     The locking bar  420  can generally include a body  454  having a finger  456  extending therefrom. A catch  458  can be formed on a terminal end of the finger  456 . The locking bar  420  can be formed of biocompatible metallic material, such as titanium for example. The body  454  can further include a leading end  460  and a trailing end  462 . 
     Attaching the respective first and second bearing components  416  and  418  to the tibial tray  414  according to one example of the present teachings will now be described. Once a surgeon has selected a first and second bearing component  416  and  418  that satisfies the given needs of a particular patient (see also kit  600 ,  FIG. 21 ), they are independently located onto the medial and lateral portions  436  and  438  of the tibial tray  414 . In this regard, the posterior engagement tabs  440  of the tibial tray  414  can locate into the respective engagement grooves  427  and  433  of the first and second bearing components  416  and  418 . In some examples, the respective first and second bearing components  416  and  418  may be advanced posteriorly, such that the engagement tabs  440  can lock into the engagement grooves  427  and  433 . Concurrently, the anterior tabs  443  can locate into the anterior engagement grooves  427  and  433  of the first and second bearing components  416  and  418 . Next, a surgeon can slidably advance the leading end  460  of the locking bar  420  through the respective anterior channels  428  and  434  of the first and second bearing components  416  and  418 . Concurrently, a portion of the body  454  can locate along a posterior side of the anterior engagement bridge  442  while the finger  456  locates around an anterior side of the anterior engagement bridge  442 . The locking bar  420  can be further advanced until the catch  458  on the finger  456  can locate around the wall  446  on the anterior engagement bridge  442 . 
     With reference now to  FIG. 20 , another tibial tray  514  constructed in accordance to the present teachings is shown. The tibial tray  514  generally includes an inferiorly extending stem  516 . The tibial tray  514  can be a full tibial tray that can be particularly suited for examples where a central slot (such as the slot  422 ) for accommodating an ACL is not needed. The tibial tray  514  includes posterior engagement tabs  540  and an anterior engagement bridge  542 . Anterior locating tabs  543  can be formed on the tray  514 . The anterior engagement bridge  542  can include a track  544 . The tibial tray  514  can be configured to selectively and intraoperatively secure independent medial and lateral bearings, such as the bearings  416  and  418  disclosed herein. 
     Turning now to  FIG. 21 , a kit  600  is shown having a collection of medial and lateral bearings that provide unique articulations, sizes and thicknesses (i.e., D 1 , D 2 , D 3 , etc.) and incorporate either a fixed or mobile configuration on the lateral and medial sides. The kit  600  further includes the bicruciate retaining tibial tray and the posterior cruciate retaining tray. As disclosed herein, the kit can be particularly suited for allowing a surgeon the opportunity to intraoperatively select a given medial and/or lateral bearing component and tibial tray that is particularly suited for a given patient. It is contemplated that with the kit  600 , a surgeon can also utilize the components during a revision surgery where the level of constraint needs to be increased. In this regard, a surgeon may only desire to change some components while leaving others unchanged. 
     As used herein, the terms superior, superiorly, superior direction are used to generally refer to the anatomical meaning, such as higher in place or position or generally situated above. Similarly, the terms inferior, inferiorly, inferior direction are used to generally refer to the anatomical meaning, such as lower in place or position or generally situated below. 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.