Medial knee injuries are prevalent, especially in young athletes. A detailed history and physical examination are needed to accurately diagnose injuries to the superficial medial collateral ligament (sMCL), deep medial collateral ligament (dMCL), and posterior oblique ligament (POL). The mechanism of medial knee injury often involves a coupled valgus and external rotation force with pain and tenderness across the medial joint line. Valgus stress radiographs assist with the diagnosis of medial knee injuries based on the quantitative extent of medial joint gapping. Specifically, 3.2 mm of increased medial gapping is observed with an isolated grade-III sMCL injury and greater than 9.8 mm of gapping indicates a complete medial knee injury. Nonoperative treatment is recommended for grade-I and II medial knee injuries. Patients with chronic medial knee instability, or a complete tear of the medial knee structures, may require operative treatment. Anatomic surgical techniques have proven to be highly effective in restoring functional knee stability.