Injuries to the medial side of the knee are the most common knee ligament injuries. The majority of injuries occur in young athletes during sporting events, with the usual mechanism involving a valgus contact, tibial external rotation, or a combined valgus and external rotation force delivered to the knee. Although most complete grade III medial knee injuries heal, some do not, which can lead to continued instability. For these patients, a thorough understanding of the presenting history and a physical examination are important because these injuries can often be confused with posterolateral corner injuries. The main anatomic structures of the medial side of the knee are the superficial medial collateral ligament, deep medial collateral ligament, and posterior oblique ligament. In addition, accurately locating 3 bony prominences over the medial aspect of the knee-the adductor tubercle, gastrocnemius tubercle, and medial epicondyle-is important to conduct a proper physical examination and for surgical repairs and reconstructions. Clinical diagnosis of medial knee injuries is primarily performed viathe application of a valgus stress in full extension and at 30° of knee flexion. In addition, an examination of the amount of anteromedial tibial rotation is performed at 90° of flexion, while the dial test, performed at 30° and 90° of flexion, is important because it evaluates for rotational abnormalities. Valgus stress radiographs are useful to objectively determine the amount ofmedial compartment gapping and to discern whether there is medial or lateral compartment gapping when a medial or posterolateral corner knee injury cannot be differentiated, especially with a chronic injury. The majority of acute grade III medialknee injuries will heal after a nonoperative rehabilitation program. In most instances when there is a knee dislocation or multiligament injury, a primary repair with sutures may be indicated. In severe midsubstance injuries or chronic medial kneeinjuries, an anatomic medial knee reconstruction with grafts may be indicated. Rehabilitation principles for acute medial kneeinjuries involve controlling edema, regaining range of motion, and avoiding any significant stress on the healing ligaments. A well-guided rehabilitation program can result in excellent functional outcomes in the majority of patients.