TOTAL KNEE IMPLANT PROSTHESIS ASSEMBLY AND METHOD

Abstract

A total knee implant prosthesis is disclosed. The total knee implant prosthesis includes a tibial component including a pair of bearing surfaces and a post positioned between the bearing surfaces, and a femoral component configured to rotate relative to the tibial component. The femoral component includes a pair of condyles sized and shaped to articulate on the bearing surfaces and a cam positioned between the pair of condyles. The cam engages the post at a first contact point when the femoral component is at 0 degrees of flexion and engages the post at a second contact point located lateral of the first contact point when the femoral component is at a first degree of flexion greater than 0 degrees. The cam is disengaged from the post when the femoral component is at a second degree of flexion greater than the first degree of flexion.

Claims

1. An orthopaedic prosthesis comprising: a tibial component configured to be coupled to a surgically-prepared proximal end of a patient's tibia, the tibial component including a medial bearing surface, a lateral bearing surface, and a post positioned between the medial bearing surface and the lateral bearing surface, wherein the post includes an anterior side and a posterior side opposite the anterior side, and wherein the medial bearing surface and the lateral bearing surface are asymmetrical relative to each other; and a femoral component to be coupled to a surgically-prepared distal end of a patient's femur, the femoral component including a medial condyle configured to articulate on the medial bearing surface of the tibial component and a lateral condyle configured to articular on the lateral bearing surface of the tibial component, wherein the medial bearing surface includes a distal-most point positioned posteriorly of an anterior-most point of the anterior side of the post and anteriorly of a posteriorly-most point of the posterior side of the post.

2. The orthopaedic prosthesis of claim 1, wherein the anterior-most point of the anterior side of the post lies on a medial-lateral centerline of the post when the tibial component is viewed in a transverse plane, wherein the medial-lateral centerline extends in an anterior-posterior direction.

3. The orthopaedic prosthesis of claim 1, wherein distal-most point is positioned posteriorly of the anterior-most point of the anterior side of the post by a distance of at least six millimeters.

4. The orthopaedic prosthesis of claim 1, wherein distal-most point is positioned posteriorly of the anterior-most point of the anterior side of the post by a distance of at least ten millimeters.

5. The orthopaedic prosthesis of claim 1, wherein the medial bearing surface includes an anterior end and a posterior end opposite the anterior end, and wherein the distal-most point of the medial bearing surface is located closer to the posterior end than the anterior end when the tibial component is viewed in a sagittal plane.

6. The orthopaedic prosthesis of claim 5, wherein distal-most point of the medial bearing surface is positioned a first distance from the anterior end and a second distance from the posterior end when the tibial component is viewed in the sagittal plane, the first distance being greater than the second distance.

7. The orthopaedic prosthesis of claim 1, wherein the femoral component further includes a cam positioned between the medial and lateral condyles, wherein the cam is configured to engage the post of the tibial component when the femoral component is positioned in a full extension position on the tibial component and disengage the post when the femoral component is positioned in a full flexion position, and wherein the cam is configured to engage a contact point on the post and wherein the contact point moves laterally along the post when the femoral component is rotated from the full extension position toward a full flexion position.

8. The orthopaedic prosthesis of claim 1, wherein the anterior side of the post is angled to face toward the medial bearing surface and away from the lateral bearing surface when the tibial component is viewed in a transverse plane.

9. The orthopaedic prosthesis of claim 1, wherein tibial component has a medial-lateral centerline when the tibial component is viewed in a first transverse plane and the post has a medial-lateral centerline, when the post is viewed in the first transverse plane, that is laterally offset from the medial-lateral centerline of the tibial component when the tibial component is viewed in the first transverse plane.

10. An orthopaedic prosthesis comprising: a tibial component configured to be coupled to a surgically-prepared proximal end of a patient's tibia, the tibial component including a medial bearing surface located on a medial side of the tibial component, a lateral bearing surface located on a lateral side of the tibial component, and a post positioned between the medial bearing surface and the lateral bearing surface, wherein the medial bearing surface and the lateral bearing surface are asymmetrical relative to each other; and a femoral component to be coupled to a surgically-prepared distal end of a patient's femur, the femoral component including a medial condyle configured to articulate on the medial bearing surface of the tibial component and a lateral condyle configured to articular on the lateral bearing surface of the tibial component, wherein the tibial component has a medial-lateral centerline when the tibial component is viewed in a first transverse plane and the post of the tibial component is laterally offset toward a side of the tibial component relative to the medial-lateral centerline when the tibial component is viewed in the first transverse plane.

11. The orthopaedic prosthesis of claim 10, wherein the post has a medial-lateral centerline when the post is viewed in the first transverse plane that is laterally offset from the medial-lateral centerline of the tibial component when the tibial component is viewed in the first transverse plane.

12. The orthopaedic prosthesis of claim 11, wherein the medial-lateral centerline of the post is laterally offset toward the medial side of the tibial component.

13. The orthopaedic prosthesis of claim 11, wherein the medial-lateral centerline of the post is laterally offset toward the lateral side of the tibial component.

14. The orthopaedic prosthesis of claim 10, wherein the post is laterally offset toward the medial side of the tibial component.

15. The orthopaedic prosthesis of claim 10, wherein the post is laterally offset toward the lateral side of the tibial component.

16. The orthopaedic prosthesis of claim 10, wherein the medial bearing surface includes an anterior end and a posterior end opposite the anterior end, and wherein a distal-most point of the medial bearing surface is located closer to the posterior end than the anterior end when the tibial component is viewed in a sagittal plane.

17. The orthopaedic prosthesis of claim 16, wherein distal-most point of the medial bearing surface is positioned a first distance from the anterior end and a second distance from the posterior end when the tibial component is viewed in the sagittal plane, the first distance being greater than the second distance.

18. The orthopaedic prosthesis of claim 10, wherein the femoral component further includes a cam positioned between the medial and lateral condyles, wherein the cam is configured to engage the post of the tibial component when the femoral component is positioned in a full extension position on the tibial component and disengage the post when the femoral component is positioned in a full flexion position, and wherein the cam is configured to engage a contact point on the post and wherein the contact point moves laterally along the post when the femoral component is rotated from the full extension position toward a full flexion position.

19. The orthopaedic prosthesis of claim 10, wherein the anterior side of the post is angled to face toward the medial bearing surface and away from the lateral bearing surface when the tibial component is viewed in the first transverse plane.

20. An orthopaedic prosthesis comprising: a tibial component configured to be coupled to a surgically-prepared proximal end of a patient's tibia, the tibial component including a medial bearing surface, a lateral bearing surface, and a post positioned between the medial bearing surface and the lateral bearing surface, wherein the medial bearing surface and the lateral bearing surface are asymmetrical relative to each other; and a femoral component to be coupled to a surgically-prepared distal end of a patient's femur, the femoral component including a medial condyle configured to articulate on the medial bearing surface of the tibial component and a lateral condyle configured to articular on the lateral bearing surface of the tibial component, wherein the medial bearing surface includes an anterior end, a posterior end opposite the anterior edge, and a distal-most point positioned a first distance from the anterior end and a second distance from the posterior end when the tibial component is viewed in a sagittal plane, the first distance being greater than the second distance.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The detailed description particularly refers to the following figures, in which:

[0029] FIG. 1 is an exploded perspective view of an exemplary embodiment of a replacement knee prosthesis providing anterior stabilization;

[0030] FIG. 2 is an exploded elevation view illustrating the replacement knee prosthesis of FIG. 1;

[0031] FIG. 3 is a cross-sectional elevation view taken along the line 3-3 in FIG. 1 illustrating the femoral component of the replacement knee prosthesis of FIGS. 1-2;

[0032] FIG. 4 is a cross-sectional plan view taken along the line 4-4 in FIG. 2 illustrating the femoral component of the replacement knee prosthesis of FIG. 1 in a plane extending perpendicular to the plane shown in FIG. 3;

[0033] FIG. 5 is a plan view illustrating the tibial component of the replacement knee prosthesis of FIG. 1;

[0034] FIG. 6 is a cross-sectional plan view taken along the line 6-6 in FIG. 2 illustrating the tibial component of the replacement knee prosthesis of FIG. 1;

[0035] FIG. 7 is an elevation view taken along the line 7-7 in FIG. 1 illustrating the tibial component of the replacement knee prosthesis of FIGS. 1-2 in a plane extending perpendicular to the plane shown in FIG. 5;

[0036] FIG. 8 is an elevation view of the replacement knee prosthesis of FIG. 1 illustrating the relative positions of the femoral component and the tibial component over a range of flexion;

[0037] FIG. 9 is a cross-sectional elevation view illustrating the replacement knee prosthesis of FIG. 1 at about 0 degrees of flexion;

[0038] FIG. 10 is a cross-sectional plan view illustrating the replacement knee prosthesis of FIG. 9 in a plane extending perpendicular to the plane of FIG. 9 at about 0 degrees of flexion;

[0039] FIG. 11 is a cross-sectional elevation view similar to FIG. 9 illustrating the replacement knee prosthesis at about 7.5 degrees of flexion;

[0040] FIG. 12 is a cross-sectional plan view similar to FIG. 10 illustrating the replacement knee prosthesis at about 7.5 degrees of flexion;

[0041] FIG. 13 is a cross-sectional elevation view similar to FIGS. 9 and 11 illustrating the replacement knee prosthesis at about 15 degrees of flexion;

[0042] FIG. 14 is a cross-sectional plan view similar to FIGS. 10 and 12 illustrating the replacement knee prosthesis at about 15 degrees of flexion;

[0043] FIG. 15 is a plan view of the replacement knee prosthesis of FIG. 1 illustrating the relative positions of the femoral component and the tibial component over a range of flexion;

[0044] FIG. 16 is an anterior perspective view of the tibial component of the replacement knee prosthesis of FIG. 1;

[0045] FIG. 17 is a plan view of another exemplary embodiment of a femoral component; and

[0046] FIG. 18 is a cross-sectional elevation view taken along the line 18-18 in FIG. 17 illustrating the femoral component.

DETAILED DESCRIPTION OF THE DRAWINGS

[0047] While the concepts of the present disclosure are susceptible to various modifications and alternative forms, specific exemplary embodiments thereof have been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the concepts of the present disclosure to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

[0048] Terms representing anatomical references, such as anterior, posterior, medial, lateral, superior, inferior, etcetera, may be used throughout the specification in reference to the orthopaedic implants and orthopaedic surgical instruments described herein as well as in reference to the patient's natural anatomy. Such terms have well-understood meanings in both the study of anatomy and the field of orthopaedics. Use of such anatomical reference terms in the written description and claims is intended to be consistent with their well-understood meanings unless noted otherwise.

[0049] The exemplary embodiments of the present disclosure are described and illustrated below to encompass prosthetic knee joints and knee joint components, as well as methods of implanting and reconstructing knee joints. Of course, it will be apparent to those of ordinary skill in the art that the preferred embodiments discussed below are exemplary in nature and may be reconfigured without departing from the scope and spirit of the present invention. However, for clarity and precision, the exemplary embodiments as discussed below may include optional steps, methods, and features that one of ordinary skill should recognize as not being a requisite to fall within the scope of the present invention.

[0050] Referring now to FIG. 1, an exemplary embodiment of an orthopedic knee implant 10 for use with total arthroplasty procedures is shown. The implant 10 includes a femoral component 12 and a tibial component 14 that is configured to permit the femoral component 12 to articulate over a range of flexion. In this exemplary embodiment, the tibial component 14 comprises a tibial tray insert 18, which is configured to be attached to, for example, a tibial tray (not shown) adapted to be secured to the proximal end of a tibia. Such trays may include stems configured to be received within the intramedullary canal of the tibia. It should be appreciated that the tray may provide either a fixed bearing interface to lock the orientation of the tibial tray insert 18 with the tibial tray or a mobile bearing interface that allows the tibial tray insert 18 to move independent of the tibial tray. Additionally, in other embodiments, the tibial tray and the tibial tray insert may be combined into a single, monolithic component.

[0051] The femoral component 12 is illustratively formed from a metallic material such as cobalt-chromium or titanium, but may be formed from other materials, such as a ceramic material, a polymer material, a bio-engineered material, or the like, in other embodiments. The tibial tray insert 18 is illustratively formed from a polymer material such as an ultra-high molecular weight polyethylene (UHMWPE), but may be formed from other materials, such as a ceramic material, a metallic material, a bio-engineered material, or the like, in other embodiments.

[0052] As shown in FIG. 1, the femoral component 12 is illustratively a posterior cruciate retaining orthopedic femoral component that includes a posterior discontinuity or gap 20 between lateral and medial condyles 22, 24 to allow the femoral component to rotate between maximum extension and maximum flexion without impinging the posterior cruciate ligament (PCL), which is retained during the total arthroplasty procedure. In contrast, the anterior cruciate ligament (ACL) is sacrificed or removed during a total arthroplasty procedure. Those skilled in the art are familiar with the posterior constraint resulting from retention of the posterior cruciate ligament, whereas those skilled in the art are also familiar with the absence of anterior constraint resulting from the absence of the anterior cruciate ligament.

[0053] The exemplary femoral component 12 includes a pair of condyles 22, 24, each of which has an arcuate shape in order to allow for smooth rotation of the femur with respect to the tibia. In general, the femoral component includes an anterior portion 26 and a posterior portion 28 that are shown by the dotted line imaginary boundary line 29 in FIG. 1. The anterior portion 26 includes a front exterior face 30 having a depression 32 adapted to receive at least a portion of a patella component. The depression 32 marks the beginning of individual condyle 22, 24 formation. From the top or superior-most portion of the front face 30 downward, following the contours of the front face, the curved nature of begins to take shape and transition into individual condyles 22, 24. As the shape of the condyles 22, 24 becomes more pronounced, the condyles separate from one another, which is marked by an arcuate bridge 34 (see FIG. 3) formed at the distal end of the depression 32. In the illustrative embodiment, the arcuate bridge 34 defines the anterior end of the gap 20 between the condyles 22, 24. The femoral component 12 also includes an anterior cam 36 that is positioned posterior of, and superior to, the arcuate bridge 34. As described in greater detail below, the anterior cam 36 is configured to engage a post 38 of the tibial component 14.

[0054] The front exterior face 30 of the femoral component 12 includes an articulation surface 48 that is configured to engage a corresponding surface of a patella component. The articulation surface 48 defines the depression 32 and includes the arcuate bridge 34. At the arcuate bridge, the articulation surface 48 separates into a medial articulation surface 50 of the medial condyle 22 and a lateral articulation surface 52 of the lateral condyle 24. The surfaces 50, 52 are configured to engage with and articulate on corresponding bearing surfaces 54, 56, respectively, of the tibial component 14. The articulation surfaces 50, 52 of the condyles 22, 24 flatten out and do not exhibit a uniform arcuate shape from anterior to posterior. Additionally, as illustrated in FIG. 1, the medial condyle 22 has a maximum medial-lateral width that is larger than the maximum medial-lateral width of the lateral condyle 24. However, in the illustrative embodiment, the gap 20 has a substantially uniform width, resulting in the inner shape and contour of the condyles being substantially the same.

[0055] As shown in FIGS. 3-4, the anterior cam 36 of the femoral component 12 has a posterior surface 60 that is arcuate or rounded when the femoral component is viewed in the plane shown in FIG. 3, which may correspond to the sagittal plane of the patient's body with the femoral component 12 is implanted therein. In the illustrative embodiment, the surface 60 defines a convex curved line 62 when viewed in the plane of FIG. 3, but it should be appreciated that in other embodiments the camming surface may define a concave curved line. In still other embodiments, the camming surface may define a substantially straight line for a substantially flat or planar cam. As described above, the anterior cam 36 is positioned posterior of, and superior to, the arcuate bridge 34. As shown in FIG. 3, the anterior cam 36 is connected to the arcuate bridge 34 via a connecting surface 64 extending superiorly from the arcuate bridge 34 between the condyles 22, 24.

[0056] When viewed in the plane of FIG. 3, the medial articulation surface 50 of the femoral component 12 defines an arcuate line 66 extending from a distal-most point 68 of the medial articulation surface 50 to a superior-most point 70. In the illustrative embodiment, the distal-most point 68 of the medial articulation surface 50 lies in a plane with the boundary line 29 that marks the division of the femoral component 12 into the anterior portion 26 and the posterior portion 28. As shown in FIG. 3, the posterior-most point 72 of the medial surface 50 is positioned anterior of the distal-most point 68 of the medial articulation surface 50. In that way, the anterior cam 36 is positioned entirely in the anterior portion 26 of the femoral component 12.

[0057] As shown in FIG. 3, the curved line 62 (and hence the surface 60 in the plane of FIG. 3) has a radius 80 that extends from an origin 82 positioned anterior of, and superior to, the distal-most point 68 of the medial articulation surface 50. A pair of distances 84, 86 are defined between the point 68 and the origin 82 in the anterior-posterior direction and superior-inferior direction, respectively. In the illustrative embodiment, the anterior-posterior distance 84 is equal to about 6.25 mm. A person of ordinary skill would understand that the term about as used herein accounts for typical manufacturing or measurement tolerances present in the manufacture or use of prosthetic components. Exemplary manufacturing tolerances include 0.1 millimeters. In other embodiments, the anterior-posterior distance 84 between the origin 82 and the distal-most point 68 of the medial surface 50 may be in a range of about 0 mm to about 12 mm.

[0058] The superior-inferior distance 86 between the distal-most point 68 and the origin 82 (and also the posterior-most point 72 of the cam 36) is equal to about 12.25 mm in the illustrative embodiment. In other embodiments, the distance 86 may be in a range of about 5 mm to about 20 mm. The radius 80 of the surface 60 is illustratively equal to about 3 mm, but, in other embodiments, the radius 80 may be in a range of about 1 mm to about 6 mm. In still other embodiments, the radius 80 may be greater than 6 mm. It should be appreciated that in other embodiments the radius 80 and the distances 84, 86 may be greater or less than these ranges depending on the physical requirements of a particular patient.

[0059] Referring now to FIG. 4, the surface 60 of the cam 36 is illustratively shown as arcuate or rounded when viewed in a plane extending perpendicular to the plane shown in FIG. 3, which may correspond to the transverse plane of the patient's body with the femoral component 12 is implanted therein. In the illustrative embodiment, the surface 60 defines a convex curved line 90 that extends from a medial end 74 to a lateral end 76 when viewed in the plane shown in FIG. 4. It should be appreciated that in other embodiments the surface may define a concave curved line in the transverse plane. In still other embodiments, the posterior surface may define a substantially straight line for a substantially flat or planar cam. As described above, the cam 36 is convex and curved when viewed in either the sagittal or the transverse plane. It should be appreciated that in other embodiments the cam 36 may include any combination of convex, concave and/or flat surfaces in those planes. For example, in some embodiments, the cam 36 may be convex when viewed in the sagittal plane and concave when viewed in the transverse plane.

[0060] As shown in FIG. 4, the curved line 90 (and hence the posterior surface 60 in the plane shown in FIG. 4) has a radius 92 that extends from an origin 94. The radius 92 of the surface 60 is equal to about 33 mm in the illustrative embodiment. In other embodiments, the radius 92 may be in a range of about 10 mm to about 33 mm. In still other embodiments, the radius 92 may be greater than 33 mm.

[0061] As shown in FIG. 4, the femoral component 12 has a medial-lateral center line 96 that extends in the anterior-posterior direction. In the illustrative embodiment, the origin 94 is offset from the center line 96 in a lateral direction by a medial-lateral distance 98. The distance 98 is equal to about 3 mm. In other embodiments, the distance 98 between the origin 94 and the central axis 682 may be in a range of about 0 mm to about 6 mm. In still other embodiments, the distance 688 may be greater than 6 mm.

[0062] In the illustrative embodiment, the posterior-most point 72 is the medial-lateral mid-point of the surface 60 of the cam 36. As shown in FIG. 4, the posterior-most point 72 is offset by the same distance 98 from the center line 96. As a result, the surface 60 (and hence the cam 36) is offset laterally from the center line 96. It should be appreciated that in other embodiments the posterior-most point of the camming surface may be offset from the center line 96 less than or greater than the origin 94. For example, the origin 94 may be offset from the center line 96 while the posterior-most point of the camming surface intersects with the center line 96. It should also be appreciated that in other embodiments the radius 92 and the distance 98 may be greater or less than these ranges depending on the physical requirements of a particular patient.

[0063] In the illustrative embodiment, the center line of the gap 20 is also offset by the same distance 98 from the center line 96 of the femoral component 12. In that way, the gap 20 is laterally offset in the femoral component 12. It should be appreciated that in other embodiments the distance 98 may be greater or less than these ranges depending on the physical requirements of a particular patient. In other embodiments, the center line of the gap 20 offset from the center line by a different distance than the other structures of the femoral component 12. In still other embodiments, the center line of the gap 20 may not be offset at all.

[0064] Returning to FIG. 1, the implant 10 also includes a tibial tray insert 18. As described above, the tibial tray insert 18 includes bearing surfaces 54, 56 that are adapted to receive and engage the condyles 22, 24 of the femoral component 12. The two bearing surfaces 54, 56 are partially separated from one another by a post 38 upstanding from the tibial tray insert 18. In this exemplary embodiment, the post 38 is integrally formed with the tibial tray insert 18. However, it should be appreciated that the post 38 may be separable from the tibial tray insert 18 and its location is independent of the location/movement of the tibial tray insert.

[0065] The post 38 has an anterior surface or wall 100 that is configured to engage the posterior surface 60 of the cam 36 of the femoral component 12 when the implant 10 (and hence the knee) is at full extension and over part of flexion. As shown in FIG. 2, the post 38 also includes a curved anterior section 102 that is sized to ensure the cam 36 properly disengages from the post 38. It should be appreciated that the post 38 may include other structure that is sized and shaped to ensure the cam 36 properly disengages from the post 38.

[0066] The bearing surfaces 54, 56 are illustratively concave surfaces. Additionally, as shown in FIG. 2, the surfaces 54, 56 are asymmetrical and share a common posterior geometry before diverging as they progress anteriorly, with the lateral surface 56 having a flatter anterior section than the medial surface 54. In the illustrative embodiment, the medial surface 54 has a distal-most point 112 that is proximate to where the geometries of the surfaces 54, 56 begin to diverge. It should be appreciated that in other embodiments the surfaces 54, 56 may be symmetrical and have substantially identical geometries.

[0067] Referring now to FIG. 5, a medial-lateral center line 116 that extends in the anterior-posterior direction indicates the medial-lateral mid-line of the tibial insert 18. Another medial-lateral center line 118 that extends in the anterior-posterior direction indicates the medial-lateral mid-line of the post 38. In the illustrative embodiment, the post center line 118 is offset from and extends parallel to the center line 116 of the insert 18. A distance 120 is defined between lines 116, 118; in the illustrative embodiment, the distance 120 is equal to about 3 mm such that the post line 118 (and hence the post 38 itself) is offset in a lateral direction from the central line 116. In other embodiments, the distance 120 may be in a range of about 0 mm to about 6 mm. In still other embodiments, the distance 120 may be greater than 6 mm.

[0068] As shown in FIG. 5, the anterior wall 100 is positioned anterior of the distal-most point 112 of the medial bearing surface 54, which lies in a plane with the boundary line 29. In that way, the anterior wall 100 is positioned entirely in the anterior portion of the tibial insert 18. In the illustrative embodiment, a distance 130 extending in an anterior-posterior direction is defined between the distal-most point 112 and the anterior wall 100. The distance 130 is illustratively equal to about 6 mm; in other embodiments, the distance 130 may be in a range of 0 mm to 10 mm. In still other embodiments, the distance may be greater than 10 mm.

[0069] In the illustrative embodiment, the anterior wall 100 of the post 38 is arcuate or rounded when the post 38 is viewed in a transverse plane. As shown in FIG. 6, the anterior wall 100 defines a convex curved or arced line 140 when viewed in the transverse plane, but it should be appreciated that in other embodiments the anterior wall may define a concave arced line. In still other embodiments, the camming surface may define a substantially straight line for a substantially flat or planar surface.

[0070] The arced line 140 (and hence the anterior wall 100 in the transverse plane) has a radius 142 that extends from an origin 144. As shown in FIG. 6, a distance 146 extending in a medial-lateral direction is defined between the origin 144 and the post center line 118. In the illustrative embodiment, the distance 146 is equal to about 1.2 mm such that the origin 144 is offset from the post center line 118 in a lateral direction. In other embodiments, the distance 146 may be equal to about 0 mm to about 6 mm. In still other embodiments, the distance may be greater than 6 mm.

[0071] Due to the combination of the distances 120, 146, the origin 144 is offset laterally from the central line 116 of the tibial insert 18 by about 4.2 mm. In other embodiments, the origin 144 may be offset in a range of about 0 mm to about 12 mm.

[0072] As shown in FIG. 6, the radius 142 of the anterior wall 100 is illustratively equal to about 15 mm, but, in other embodiments, the radius 142 may be in a range of about 10 mm to about 15 mm. In still other embodiments, the radius may be greater than 15 mm. It should be appreciated that in other embodiments the radius 142 and the distances 120, 130, and 146 may be greater or less than these ranges depending on the physical requirements of a particular patient.

[0073] In the illustrative embodiment, the anterior wall 100 of the post 38 is angled toward the medial bearing surface 54. As shown in FIG. 6, the arced line 140 defined by the anterior wall 100 intersects the post center line 118 at a point 150, and a straight imaginary line 152 extends from the origin 144 through the point 150 such that an angle is defined between the imaginary line 152 and the post center line 118. In the illustrative embodiment, the angle is equal to about 4.6 degrees, indicating the amount that the anterior wall 100 is angled toward the medial bearing surface 54.

[0074] Referring now to FIG. 7, the anterior wall 110 of the tibial component 14 is arcuate or rounded when the tibial component is viewed in a sagittal plane. In the illustrative embodiment, the anterior wall 100 defines a concave curved line 160 when viewed in the sagittal plane, but it should be appreciated that in other embodiments the anterior wall may define a concave curved line. In still other embodiments, the anterior wall may define a substantially straight line for a substantially flat or planar post.

[0075] The curved line 160 (and hence the anterior wall 100) has a radius 162 that extends from an origin 164. The radius 162 of the anterior wall 100 is illustratively equal to about 25 mm, but, in other embodiments, the radius 162 may be in a range of about 3 mm to about 25 mm. In still other embodiments, the radius may be greater than 25 mm. It should be appreciated that in other embodiments the radius may be greater or less than these ranges depending on the physical requirements of a particular patient.

[0076] Referring now to FIGS. 8-16, the femoral component 12 is configured to articulate on the tibial insert 18 during use. During a predetermined range of flexion, the cam 36 of the femoral component 12 contacts the post 38 of the tibial insert 18. For example, when the implant 10 is at a larger degree of flexion, the cam 36 is not in contact with the post 38. However, when the implant is at extension or is otherwise not in flexion (e.g., a flexion of about 0 degrees), the cam 36 is configured to contact the post 38 to cause axial rotation of the femoral component 12 relative to the tibial insert 18 and generally pull the femoral component 12 anteriorly.

[0077] The anterior cam 36 of the femoral component 12 is illustrated in contact with the anterior wall 100 of the tibial post 38 at about 0 degrees of flexion in FIGS. 9-10. As shown in FIG. 10, a contact point 200 is defined at the point on the anterior wall 100 where the cam 36 engages the tibial post 38. The contact point 200 is illustratively located medial of the medial-lateral center line 118 of the post 38, and the femoral component 12 is angled on the tibial insert 18 toward the medial side of the assembly so that femoral component's center line 96 extends at an acute angle relative to the post center line 118 and the tibial insert center line 116. The tibial post 38 is offset laterally with the gap 20 of the femoral component 12.

[0078] As the femoral component 12 is articulated between about 0 degrees of flexion and about 7.5 degrees of flexion, the femoral component 12 rotates laterally relative to the tibial insert 18, and the contact point between the cam 36 and the post 38 moves laterally during flexion along the anterior wall 100, as shown in FIG. 12. As shown in FIG. 11, a contact point 202 is defined at the point on the anterior wall 100 where the cam 36 engages the tibial post 38. The contact point 202 is located closer to the medial-lateral center line 118 of the post 38, but the contact point 202 continues to be located medial of that line. The femoral component 12 is angled on the tibial insert 18 toward the medial side of the assembly, but a smaller angle is defined between the femoral component's center line 96 and the post center line 118 and the tibial insert center line 116. The tibial post 38 is offset laterally with the gap 20 of the femoral component 12.

[0079] As the femoral component 12 is articulated between about 7.5 degrees of flexion and 15 degrees of flexion, the femoral component 12 continues to rotate laterally relative to the tibial insert 18, and the contact point between the cam 36 and the post 38 moves laterally along the anterior wall 100 during flexion, as shown in FIG. 14. As shown in FIG. 13, a contact point 204 is defined at the point on the anterior wall 100 where the cam 36 engages the tibial post 38. The contact point 204 is illustratively located approximately on the medial-lateral center line 118 of the post 38. It should be appreciated that in other embodiments the point 204 may be located lateral of the medial-lateral center line 118 of the post 38. In such embodiments, the femoral component 12 is angled on the tibial insert 18 toward the lateral side of the assembly so that femoral component's center line 96 extends at an acute angle relative to the post center line 118 and the tibial insert center line 116. In the illustrative embodiment, however, the femoral component 12 is positioned on the tibial insert 18 so that its center line 96 extends generally parallel to the tibial insert center line 116, as shown in FIG. 14. The tibial post 38 remains offset laterally with the gap 20 of the femoral component 12

[0080] As described above, the femoral component 12 rotates relative to the tibial insert 18 in the direction indicated by arrow 210 in FIG. 15 as the component 12 is articulated from full extension (about 0 degrees of flexion) through about 15 degrees of flexion. In the illustrative embodiment, this rotation causes the femoral component 12 to rotate from a position 212 in which it faces toward the medial side of the assembly to a position 214 in which the femoral component 12 faces in the anterior direction. This rotation serves to reduce the inversion-eversion laxity of the patient's knee. The illustrative embodiment allows approximately 15 degrees of total rotation between about 0 degrees of flexion and about 15 degrees of flexion.

[0081] As described above, the location where the cam 36 contacts the post 38 moves laterally as the femoral component 12 is articulated from about 0 degrees of flexion to about 15 degrees of flexion. As shown in FIG. 16, the contact points (including points 200, 202, 204) define an arced line 218 on the anterior wall 100 of the post 38. The cam 36 moves along the arced line 218 as the femoral component 12.

[0082] Referring now to FIGS. 17-18, another embodiment of a femoral component 302 is shown. The femoral component 302 is substantially identical to the femoral component 12 described above. Unlike the femoral component 12, the surface 64 connecting the arcuate bridge 34 and the cam 36 is omitted. As shown in FIGS. 17-18, a slot 310 is defined between the arcuate bridge 34 and the anterior cam 36 to separate those components.

[0083] As described above, the cam of the femoral component and the post of the tibial component or insert are offset in the lateral direction from the respective center lines of those components. It should be appreciated that in other embodiments, the cam of the femoral component may be centered on the center line of the femoral component with the post of the tibial component offset in the lateral direction. In such embodiments, the cam width is greater than the post width.

[0084] Following from the above description and invention summaries, it should be apparent to those of ordinary skill in the art that, while the methods and apparatuses herein described constitute exemplary embodiments of the present invention, the invention contained herein is not limited to this precise embodiment and that changes may be made to such embodiments without departing from the scope of the invention as defined by the claims. Additionally, it is to be understood that the invention is defined by the claims and it is not intended that any limitations or elements describing the exemplary embodiments set forth herein are to be incorporated into the interpretation of any claim element unless such limitation or element is explicitly stated. Likewise, it is to be understood that it is not necessary to meet any or all of the identified advantages or objects of the invention disclosed herein in order to fall within the scope of any claims, since the invention is defined by the claims and since inherent and/or unforeseen advantages of the present invention may exist even though they may not have been explicitly discussed herein.