Corpus: Patellar retinaculum

The patellar retinaculum is a retaining ligament of the kneecap and is part of the outer layer of the joint capsule of the knee joint.

The patellar retinaculum has two parts:

• The externally located lateral patellar retinaculum is a fibrous structure formed from parts of the aponeurosis of the vastus lateralis muscle and the rectus femoris muscle as well as fibers of the iliotibial tract. The ligament runs laterally past the patella, sending fibers to the lateral side of the kneecap and to the fibular collateral ligament. It finally attaches laterally to the tibial tuberosity.
• The inner medial patellar retinaculum is formed from the aponeurosis of the vastus medialis muscle. It runs medially past the patella and sends fibers to the medial side of the kneecap and to the tibial collateral ligament. Further distally, it attaches medially to the tibial tuberosity.

Some authors further differentiate the medial and lateral parts of the patellar retinaculum into longitudinal and transverse fibers:

• The transverse lateral patellar retinaculum consists of transverse fibers that originate from the iliotibial tract and attach to the lateral edge of the patella. It has no direct connection to the lateral femoral epicondyle. The so-called Kaplan fibers (Kaplan 1958) connect the retinaculum with the lateral condyle.
• The transverse medial patellar retinaculum can only be differentiated in approx. 30 % (Blauth and Tillmann 1983) of people. This inconsistent structure runs from the medial epicondyle of the femur to the medial edge of the patella.

The patellar retinaculum is part of the patella's supporting apparatus and, together with the patellar ligament, reinforces the anterior parts of the joint capsule. As part of the quadriceps femoris muscle tendon, it contributes to knee joint extension.

The transverse fibers of the medial patellar retinaculum are particularly relevant for the stability of the patella. The physiological valgus position of the knee joint causes the patella to move laterally, and the fibers of the medial patellar retinaculum counteract this lateral movement.