Patella

The patella (kneecap) is a sesamoid bone embedded in the quadriceps tendon that improves the mechanical efficiency of knee extension. By increasing the moment arm of the quadriceps force, the patella reduces the muscle force required to extend the knee by approximately 33–50%. It also protects the anterior knee joint from direct trauma.

The patella is located at the anterior aspect of the knee joint, within the quadriceps femoris tendon. Its posterior surface articulates with the femoral trochlea, forming the patellofemoral joint. Superiorly the quadriceps tendon attaches to it, and inferiorly the patellar tendon (ligament) connects it to the tibial tuberosity. It is the largest sesamoid bone in the human body.

Common patella injuries include patellar fractures (from direct impact or forceful quadriceps contraction), patellar dislocation (usually lateral, common in young females), and patellofemoral pain syndrome (runner's knee), characterized by anterior knee pain during activities like climbing stairs or squatting. Chondromalacia patellae refers to softening and deterioration of the patellar articular cartilage.