The knee joint (lat. articulatio genus), trochoginglymus by mechanics, is the largest and most complex joint of the human body. Ligaments are the connective tissue that connects bones and are passive stabilizers of the joint. The medial and lateral collateral ligaments are the most important structures of the knee joint that ensure valgus and varus stability of the knee. Injuries to these ligaments can cause permanent pain and constant re-injury. A "valgus stress test" is performed to diagnose a medial collateral ligament injury. Injuries of the first degree indicate only stretching of ligament fibers, in the second degree of injury there is a rupture of several ligament fibers (partial rupture), and in the third degree of injury, there is a complete rupture of ligament fibers (total rupture). Treatment of the first and second degree of injury is conservative, and in the third degree, surgery is sometimes performed. The general principles of rehabilitation refer to the control of edema, to the activation of the quadriceps femoris as soon as possible after the injury, and work should be done to restore the maximum range of motion and adequate muscle strength as soon as possible. Based on physiotherapy assessment, the patient will perform a range of motion exercises, resistance and non-resistance exercises, stretching exercises, relaxation exercises, and proprioception exercises.