The knee joint is one of the largest, most complex joints in the human body. It’s made up of the articulation surfaces of three bones – the femur (thigh bone), the tibia (shinbone), and the patella (kneecap). The knee has active (static) and passive (dynamic) stabilizers. The passive ones are the bones and ligaments that hold the joint together, while the active ones are the muscles and their respective tendons that enable the joint to move.

The knee joint has a large number of ligaments to stabilize it. Among them are the cruciate ligaments (ACL – anterior cruciate ligament and PCL – posterior cruciate ligament). These connect the femur to the tibia and prevent the lower leg from sliding forwards or backwards relative to the upper leg. The ACL is the most crucial ligament because it’s always providing stability, regardless of whether you’re sleeping or being physically active. The collateral ligaments (MCL – medial collateral ligament and LCL – lateral collateral ligament) are situated along the medial and lateral part of the knee and prevent it from collapsing to the side, laterally or medially. The medial and lateral retinacula are two ligaments that go around the patella on either side, stabilizing its position. The last big ligament is the lateral ligament, which passes over the front of the patella and attaches to the tibia, just below the knee, acting as an extension of the quadriceps tendon. It provides additional stability to the patella and knee joint. The medial patellofemoral ligament (MPFL) is a smaller ligament that connects the patella to the femur. 

The knee’s active stabilizers are all of the muscles in the leg involved in knee movement. This includes the quadriceps muscle at the front of the thigh, as well as the hamstring group (biceps femoris, semimembranosus, semitendinosus), and the calf muscles (tibialis anterior/posterior, triceps surae, peroneus anterior/posterior), involved in moving the joint along its flexion-extension axis. 

The knee ligaments can suffer trauma both due to contact and due to noncontact forces. Based on its severity the injury can be classified into three grades: grade 1 – stretched but still intact; grade 2 – partial tearing; grade 3 – a complete tear. The severity will inform the rehabilitation methods, as well as the type and intensity of the exercises required for a full recovery. Play Reha’s programs cover individualized progressions, taking into account the patient’s needs, and the specifics and complexities of every type of knee ligament injury.