Knee prosthesis

1. A knee joint prosthesis assembly comprising:

a femoral component having a medial and a lateral condyle portion connected by a patellar track portion, the femoral component forming an opening between the medial and lateral condyles;

a unitary tibial component having a medial portion that includes a first engagement structure and a lateral portion that includes a second engagement structure;

a medial bearing having a third engagement structure formed thereon that selectively engages the first engagement structure; and

a lateral bearing separately formed and independent from the medial bearing and having a fourth engagement structure formed thereon that selectively engages the second engagement structure;

wherein one of the medial and lateral bearings is fixed relative to the tibial component and the other of the medial and lateral bearings is a mobile bearing component;

wherein the mobile bearing component includes:

a fixed portion having a superior surface configured to cooperate with one of the medial or lateral condyle portions of the femoral component, and having the third engagement structure or the fourth engagement structure that is configured to statically engage the tibial component; and

a mobile bearing portion having a superior articulating surface configured to cooperate with said medial or lateral condyle portions of the femoral component, said mobile bearing portion being configured to slidably advance along a superior surface of the tibial component.

2. The knee joint prosthesis of claim 1 wherein the fixed portion defines a pocket that receives and confines the mobile bearing portion therewithin.

3. The knee joint prosthesis of claim 2 wherein the mobile bearing portion is formed of a polymeric material and includes a metallic layer of material disposed around a perimeter thereof.

4. The knee joint prosthesis of claim 3 wherein the mobile bearing portion comprises a pair of tabs extending therefrom that communicate with the fixed portion during movement of the mobile bearing portion.

5. The knee joint prosthesis of claim 4 wherein the fixed portion defines a pair of complementary channels formed thereon that guide the tabs of the mobile bearing portion.

6. The knee joint prosthesis of claim 4 wherein the tabs extend from opposite sides of the mobile bearing portion.

7. The knee joint prosthesis assembly of claim 2 , wherein the mobile bearing portion includes an outer perimeter surface extending from a superior articulating surface thereof, a surrounding wall of the pocket surrounds the outer perimeter surface of the mobile bearing portion.

8. The knee joint prosthesis of claim 1 wherein the mobile bearing portion is formed of polyetheretherkatone (PEEK).

9. The knee joint prosthesis of claim 1 wherein the mobile bearing portion is formed of polyethylene.

10. A knee joint prosthesis assembly comprising:

a femoral component having a medial and a lateral condyle portion connected by a patellar track portion, the femoral component forming an opening between the medial and lateral condyles;

a unitary tibial component having a medial portion that includes a first engagement structure and a lateral portion that includes a second engagement structure;

a medial bearing having a third engagement structure formed thereon that selectively engages the first engagement structure; and

a lateral bearing separately formed and independent from the medial bearing and having a fourth engagement structure formed thereon that selectively engages the second engagement structure;

wherein one of the medial and lateral bearings is a mobile bearing component having a fixed bearing portion that defines a closed pocket, and a mobile bearing portion disposed and confined for movement within the closed pocket such that the mobile bearing portion is surrounded by the closed pocket, wherein the fixed bearing portion has a superior surface configured to cooperate with one of the medial or lateral condyle portions of the femoral component; and

wherein the mobile bearing portion having a superior articulating surface configured to cooperate with said medial or lateral condyle portions of the femoral component, said mobile bearing portion being configured to slidably advance along a superior surface of the tibial component.

11. The knee joint prosthesis of claim 10 wherein the mobile bearing portion is formed of a polymeric material and includes a metallic layer of material disposed around a perimeter thereof.

12. The knee joint prosthesis of claim 10 wherein the mobile bearing portion comprises a pair of tabs extending therefrom that communicate with the fixed portion during movement of the mobile bearing portion.

13. The knee joint prosthesis of claim 12 wherein the fixed portion defines a pair of complementary channels formed thereon that guide the tabs of the mobile bearing portion.

14. The knee joint prosthesis of claim 12 wherein the tabs extend from opposite sides of the mobile bearing portion.

15. The knee joint prosthesis of claim 10 wherein the mobile bearing portion is formed of polyetheretherkatone (PEEK).

16. The knee joint prosthesis of claim 10 wherein the mobile bearing portion is formed of polyethylene.

17. The knee joint prosthesis of claim 10 wherein the tibial component is U-shaped and is adapted to accommodate an anterior cruciate ligament.

18. The knee joint prosthesis assembly of claim 10 , wherein the closed pocket extends through the fixed bearing from a superior end to an inferior end thereof to permit an inferior surface of the mobile bearing portion to abut the unitary tibial component.