The medial patellar ligament is a connective tissue that consists of transverse fibers (fibers that run horizontally). These fibers attach and course from the superficial medial collateral ligament toward the patellar bone, or kneecap. The superficial medial collateral ligament connects the bottom of the femur (thighbone) to the top of the tibia (shinbone). The medial patellar ligament originates at the medial epicondyle (an area of bone at the top of the femur) and medial collateral ligament (MCL), an important ligament located on the inside of the knee. The medial patellar ligament is located in the second layer of the knee.

Patellar instability, or unstable kneecap, is a common condition of the medial patellar ligament where the kneecap is out of its proper place. This condition can result in pain, swelling, and difficulty using the knee. Rupturing, or tearing, of the medial patellar ligament can be the cause of this issue.

When the medial patellar ligament ruptures, it is typically caused by the lateral dislocation of the patella. This means the kneecap is displaced off to the side, which often occurs as the result of falls or sports injuries. The ligament ruptures at the femoral (thighbone) origin in most cases. Common indicators of this rupture are pain and tenderness in this ligament near the medial retinaculum, along the inner side of the knee.

Patellar instability may be treated with nonoperative management in the beginning, such as immobilization and special exercises. If that doesn’t work, surgeries may be performed, which can require the realignment of the patella.