Our Goal
Current knee replacement designs do not reproduce normal knee kinematics. Polyethylene wear is problematic in current designs.
Our Goal was to design a total knee replacement (TKR) that maintains A/P stability and axial rotation, with low polyethylene wear.
The healthy intact knee is roughly a four-bar linkage [10, 11, 12]
- Femur moves posterior on the tibia and externally rotates with flexion.
(See Figures 1 and 2a) - Femur pivots about fixed medial meniscus.
When ACL is absent
- No longer a four-bar linkages, with A/P instability increasing strain on medial meniscus, causing tears.
(O’Donohugh’s Triad) - Femur pivots about lateral compartment.
(See Figures 2b and 3)
When ACL and PCL are absent
- Instability increases, producing extreme knee dysfunction.
- Femur lacks an obligatory or preferred pivot [13].
Fig. 1. Fluoroscopic studies of healthy normal knees during weight-bearing activities show that the femur translates posteriorly and externally rotates as the knee flexes [10, 11, 12].
Fig. 2. Resected left tibial plateaus demonstrate characteristic patterns of arthritic degeneration. When the ACL is intact (4a, left), arthritic degeneration is anterior and frequently confined to the medial compartment. When the ACL is absent (4b, right), arthritic degeneration is posterior, and frequently involves both compartments [1]. 
Fig. 3. A resected left tibial plateau from a valgus knee shows the characteristic dished lateral compartment that occurs in both ACL intact and deficient arthritic knees [1].