Purpose: To investigate the effect of posterior cruciate ligament (PCL) deficiency on the kinematics and the cartilage contact characteristics of the patellofemoral joint during an in vivo single-leg lunge.
Methods: Ten patients with an isolated PCL injury in one knee and the contralateral side intact participated in the study. Magnetic resonance and dual fluoroscopic imaging techniques were used to analyze the patellofemoral kinematics and cartilage contact of the intact and the PCL-deficient knee during a quasi-static single-leg lunge from 0° to 120° of flexion.
Results: PCL deficiency significantly changed the patellofemoral kinematics between 90° and 120° of knee flexion (P < 0.007): an increased patellar flexion angle by 10.7° on average and a decreased lateral shift (on average −1.9 mm), patellar tilt (approximately −2.7°), and valgus rotation (approximately −1.8°) were observed in the PCL-deficient knee compared with the intact contralateral joint. The changes in patellofemoral kinematics resulted in significant changes in patellofemoral cartilage contact (P < 0.007). PCL deficiency caused a distal (approximately −3.3 mm) and medial (approximately + 2.7 mm) shift of cartilage contact from 75° to 120° of flexion.
Conclusion: The altered tibiofemoral kinematics that were previously described in PCL deficiency resulted in changes in patellofemoral joint function at flexion angles greater than 75°. This abnormal loading of the patellofemoral joint might predispose the patellofemoral cartilage to degenerative changes. Because we did not detect differences in the patellofemoral joint behavior of the intact and the PCL-deficient knee between 0° and 60° of flexion, rehabilitation exercises might be safely performed in this range of flexion. On the other hand, repetitive deep knee squats should be avoided in PCL-deficient patients, so as not to excessively disturb the patellofemoral cartilage contact kinematics.