Patellofemoral Joint

The patellofemoral joint is the articulation between the patella, or kneecap, and the trochlear surface at the front of the distal femur. Specifically, the cartilage-covered posterior surface of the patella contacts the femoral trochlea, an articular surface that includes the trochlear groove and surrounding facets. The patellofemoral joint is part of the knee joint but is distinct from the tibiofemoral articulation between the femur and tibia .^1,2

The patella forms part of the knee extensor mechanism. It receives force from the quadriceps muscles through the quadriceps tendon and transmits that force toward the tibia through the patellar tendon. By increasing the effective moment arm of the extensor mechanism, the patella improves its mechanical leverage and contributes to the production and control of knee extension .¹

Movement of the patella relative to the femur is often described as patellar tracking. As the knee bends, the patella progressively engages with and moves along the femoral trochlea. Its exact position and motion are influenced by the shapes of the patella and trochlea, muscle forces, and surrounding soft tissues, including ligaments and retinacular structures .^1,2

Because contact between the patella and femur changes as the knee moves, the location and size of the articular contact area also change through the range of knee flexion. The patellofemoral joint therefore functions as a moving, load-bearing interface within the knee extensor mechanism rather than as a fixed connection between the two bones .¹