The knee ligaments are mainly 4 ligaments: medial collateral ligament, lateral collateral ligament, anterior cruciate ligament and posterior cruciate ligament. 1. Medial collateral ligament: It is the most important ligament, which is between the medial epicondyle of the femur and the medial condyle of the tibia, and includes two layers of fibers, deep and shallow, which are particularly tough. It plays an important role in the stability of the joint. When the medial ligament is damaged, the knee joint will move to the inside of the knee. 2. Lateral collateral ligament: It is a tendinous structure attached to the fibular tuberosity. When the lateral collateral ligament is injured, the knee joint moves to the outside of the knee. 3. Anterior cruciate ligament: This ligament is tightest when the knee is fully flexed and the tibia is internally rotated, preventing the tibia from moving forward. 4. Posterior cruciate ligament: This ligament runs from the medial aspect of the intercondylar fossa of the femur to the posterior aspect of the intercondylar ridge of the tibia. This ligament prevents the tibia from moving backward when the knee is flexed.