A biomechanical analysis of joint contact forces in the posterior cruciate deficient knee.

The approach to the posterior cruciate deficient knee is controversial. The purpose of this study is to document the biomechanical changes in the static cadaveric knee model with simulated physiological loads. Nine fresh cadaveric knees from young donors (aged under 45 years) were mounted on a materials testing machine. Loading was carried out at 0 degrees, 30 degrees and 60 degrees to 1.5 kN with low-pressure sensitive Prescale film (Fuji; Tokyo, Japan) inserted through arthrotomies into the medial and lateral compartments. Computerized analysis of the imprints on the film was then carried out. Tests were then repeated after cutting the posterior cruciate ligament (PCL). Results demonstrate a statistically significant posterior subluxation of the tibia on the femur at 60 degrees flexion. This causes a significant increase in contact pressure and pressure concentration on the medial compartment of the knee after cutting the PCL. This may help explain the long-term degenerative changes observed in the medial femoral condyle after cutting the PCL.