The Science of Knee Pain
Patellofemoral pain syndrome involves dysfunction at the interface where your kneecap (patella) meets your thigh bone (femur). The condition typically develops when your patella doesn't track properly in its groove during knee movement, creating abnormal pressure and stress on the joint cartilage. The patella normally glides smoothly in the trochlear groove of the femur, but when muscle imbalances or structural factors alter this tracking, certain areas of cartilage experience increased compression. This can lead to irritation of pain-sensitive structures including the joint capsule, synovium, and subchondral bone. Research shows that people with patellofemoral pain often have altered biomechanics during functional activities, with changes in how forces are distributed across the joint during weight-bearing movements like squatting, stair climbing, and landing from jumps.
Contributing Factors
Your patella acts like a pulley to increase the mechanical advantage of your quadriceps muscles. When this system isn't working optimally, several biomechanical factors contribute to the problem.
Hip weakness, particularly in the gluteus medius and gluteus maximus, often allows your thigh to collapse inward during activities. This creates a valgus angle at the knee that pulls your patella laterally, increasing stress on the lateral facet.
Quadriceps imbalances, especially weakness in the vastus medialis oblique (VMO) relative to the vastus lateralis, can contribute to poor patellar tracking. The VMO is crucial for pulling the patella medially and preventing lateral drift.
Your foot mechanics also play a role - excessive pronation can create internal rotation of the tibia, which alters the angle of pull from your quadriceps and affects patellar tracking. Tight structures like the iliotibial band, lateral retinaculum, or hip flexors can create additional forces that pull the patella out of optimal alignment.