Luxation of the patella

Patellar Luxation

The patella is located at the front of the knee joint and is part of it. It’s attached to the quadriceps femoris tendon at the top and to its own tendon below, which connects it to the tibia. During extension, it is pulled up by the quadriceps femoris tendon, and slides over the femur.

The patella (or ‘kneecap’, as it is colloquially known) is stabilized by ligaments that keep it in place, allowing it to move up and down without slipping inward or outward. The medial (inner) and lateral (outer) retinacula are two bands of fascia that come out of the medial and lateral portions of the quadriceps femoris muscle. Their role is to stabilize the patella and the knee joint capsule. The primary stabilizer of the patella also stabilizes the joint and is known as the medial patellofemoral ligament (MPFL). This ligament is situated on the medial side of the knee and connects the patella to the femur. It keeps the patella in its proper place and prevents it from slipping out. 

When one of the above structures is injured, the patella might slip out of place. Should the MPFL tear, the patella destabilizes and certain movements might cause it to luxate. Often a dislocated patella occurs after an acute contusion of the MPFL – this can be due to a partial or complete tear; degenerative processes in the knee, its joint or bone tissue; deficient muscle strength. These injuries are common after a car crash or falling directly on your knee, but they may also occur during everyday activities like squatting, exiting a vehicle, walking, etc. Over time the damage can build up and make the patella chronically unstable. Reasons for such chronic instability include muscular weakness, a genetic predisposition, or natural degenerative processes.

Patellar luxation can be conservatively or surgically treated, depending on the case. Reconstruction of the MPFL is done surgically with the help of an arthroscope, whereby the ligament is either sutured at the tear or is completely anatomically reconstructed, which is the preferred method today. Reconstruction can be done by itself or it can be combined with other procedures, depending on the severity of the injury. Other procedures include releasing the lateral ligament, reconstructing or cleaning up cartilage, and ACL reconstruction, among others.

Rehabilitation after MPFL reconstruction is similar to conservative treatment. It focuses on strengthening the medial side of the quadriceps, knee stabilization exercises, etc. The process is slow however. Recovering and maintaining the range of motion of the knee should be done slowly and carefully, especially when it comes to knee flexion.

Prevention: timely and proper treatment of knee injuries; proper muscle strength management, to prevent an imbalance or weakness in the upper leg.