Biomechanical issues in patellofemoral joint rehabilitation

Specific knowledge of the biomechanics of the patellofemoral joint is crucial for successful nonoperative or postsurgical rehabilitation. The biomechanical aspects of different situations should be considered when designing an exercise program. Joint reaction forces, contact area, and contact stress are dependent on flexion angle and exercise situations. In weight-bearing activities, the amount of knee flexion directly influences the magnitude of quadriceps muscle force, which affects the magnitude of patellofemoral joint reaction forces. Open and closed chain exercises should be performed within a safe range of motion to allow quadriceps activation while minimizing patellofemoral joint reaction forces. The isolated knee extension (90 degrees-40 degrees), the squat (0 degrees-30 degrees-60 degrees), and the leg press (0 degrees-30 degrees-60 degrees) are the three main exercise situations in the acute rehabilitation phase. Controlled body positions and low levels of pain and symptoms should also be emphasized to achieve a functional progression, focusing on neuromuscular control.