Which of the following is a biomechanical factor contributing to patellofemoral syndrome?

• A. Tight hamstrings
• B. Weak vastus medialis
• C. Patellar tendon rupture
• D. Medial collateral ligament sprain

Answer: (B)

Patellofemoral pain in this context comes from abnormal tracking of the patella within the femoral groove during knee bending, driven by muscle balance around the knee. The vastus medialis, especially its oblique fibers, normally acts as the medial stabilizer pulling the patella toward the inside. When this muscle is weak, the patella loses medial support and tends to track laterally, increasing pressure on the lateral patellofemoral cartilage. That excess lateral contact pressure explains the typical pain with stairs, squatting, and bending the knee.

So weak Vastus Medialis is the key biomechanical factor because it directly disrupts patellar tracking and increases joint stress. While other issues like tight hamstrings can influence knee mechanics, they do not specifically account for the focal maltracking and increased lateral contact pressure at the patellofemoral joint the way this weakness does. Patellar tendon rupture and MCL sprain are acute injuries, not chronic biomechanical contributors to patellofemoral pain.