The patellar ligament is an extension of the quadriceps tendon. It extends from the patella, otherwise known as the kneecap. A ligament is a type of fibrous tissue that usually connects two bones.

Specifically, the ligament connects the patella to the top of the tuberosity (a ridge-like prominence) of the tibia, or shinbone. Above the kneecap, the tendon of the quadriceps femoris muscle attaches to the femur, or thighbone.

The patellar ligament not only helps keep the kneecap in its proper position but also assists in the bending of the leg at the knee. Damage to this ligament can include a complete rupture (tearing). This leads to the patella losing all support from the tibia. As a result, the leg will not extend properly. People suffering from a ruptured patellar ligament will not be able to stand, as the knee will buckle under the weight of their body.

Other ligaments within the knee include the capsular ligament and the tibial collateral ligament. Beneath these ligaments, cartilage (strong, flexible tissue) of both the tibia and the femur meet in the largest joint in the human body, the knee.