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.

2 . The knee joint prosthesis of claim 1 wherein the medial and lateral condyles of the femoral component are configured to articulate along complementary bearing surfaces of the medial and lateral bearings.

3 . The knee joint prosthesis of claim 2 wherein the medial and lateral bearings are both configured to be fixed relative to the tibial component.

4 . The knee joint prosthesis of claim 2 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 at least a portion of the mobile bearing is configured to slidably advance along an opposing surface of the tibial component.

5 . The knee joint prosthesis of claim 2 wherein both of the medial and lateral bearings are mobile bearing components that have respective portions that slidably advance along an opposing surface of the tibial component.

6 . The knee joint prosthesis of claim 4 wherein a condyle portion of the medial and lateral condyle portions that articulates on the mobile bearing component has a spherical, convex articulation surface.

7 . The knee joint prosthesis of claim 4 wherein the mobile bearing component includes a fixed portion having 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.

8 . The knee joint prosthesis of claim 7 wherein the fixed portion defines a pocket that receives and confines the mobile bearing portion therewithin.

9 . The knee joint prosthesis of claim 8 wherein the mobile bearing portion is formed of a polymeric material and includes a metallic layer of material disposed around a perimeter thereof.

10 . The knee joint prosthesis of claim 1 , further comprising:

a locking bar that selectively locates between the tibial component and the medial and lateral bearings, the locking bar cooperating with the first, second, third and fourth engagement structures and securing the medial and lateral bearings to the tibial component.

11 . The knee joint prosthesis of claim 1 wherein the tibial component is U-shaped and is adapted to accommodate an anterior cruciate ligament.

12 . The knee joint prosthesis of claim 1 wherein the tibial component has an inferiorly extending stem.

13 . The knee joint prosthesis of claim 1 , further comprising a plurality of fixed and mobile medial bearings and a plurality of separate fixed and mobile lateral bearings, wherein the plurality of medial and lateral bearings have distinct thicknesses in a superior/inferior direction.

14 . A method of implanting a knee prosthesis, the method comprising:

providing a kit of tibial trays, medial bearings and lateral bearings, the tibial trays including a bicruciate retaining tray and a posterior cruciate retaining tray, the medial and lateral bearings including a plurality of fixed and mobile medial and lateral bearings;

accessing a patient's proximal tibia and distal femur;

assessing the proximal and distal femur and at least one of an anterior cruciate ligament and posterior cruciate ligament;

selecting one of a bicruciate retaining or posterior cruciate retaining tibial tray from the kit based on the assessing;

securing the selected tibial tray to the proximal tibia;

determining whether a fixed or mobile bearing is desired for a medial and lateral side of the selected tibial tray based on the assessing;

intraoperatively and independently selecting a medial and a lateral bearing from the kit of bearings; and

securing the selected medial and lateral bearings to the selected tibial tray.

15 . The method of claim 14 wherein selecting the tibial tray comprises selecting the bicruciate retaining tray having a U-shaped slot and wherein securing the bicruciate tibial tray comprises locating an anterior cruciate ligament through the U-shaped slot.

16 . The method of claim 14 wherein securing the selected medial and lateral bearings comprises aligning respective engagement structures on the selected tibial tray with complementary engagement structures formed on the medial and lateral bearings and, further comprising:

slidably advancing a locking bar into contact with the respective engagement structures on the tray and the complementary engagement structures on the medial and lateral bearings.

17 . A knee joint prosthesis assembly comprising:

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;

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; and

a locking bar that selectively locates between the tibial component and the medial and lateral bearings, the locking bar cooperating with the first, second, third and fourth engagement structures and securing the medial and lateral bearings to the tibial component.