Human leg the femur. All four muscles unite in a common tendon inserted into the patella from where the patellar ligament extends it down to the tibial tuberosity. Fibers from the medial and lateral vasti form two retinacula that stretch past the patella on either sides down to the condyles of the tibia. The quadriceps is "the" knee extensor, but the rectus femoris additionally flexes the hip joint, and articular muscle of the knee protects the articular capsule of the knee joint from being nipped during extension. The sartorius runs superficially and obliquely down on the anterior side of the thigh, from
Articular capsule of the knee joint the suprapatellar bursa is seemingly redundant. It is however also referred to as the "suprapatellar synovial recess" as it gradually unfolds as the knee is flexed; to open up completely when the knee is flexed 130 degrees. The suprapatellar bursa is prevented from being pinched during extension by the articularis genus muscle. On the tibia, the anterior reflection and attachment of the synovial membrane is located near the cartilage. Anteriorly, the infrapatellar fat pad is inserted below the patella and between the two membranes. It extends from the lower margin of the patella above, to the infrapatellar synovial fold below.