*The superficial medial collateral ligament and other medial knee stabilizers-i.e., the deep medial collateral ligament and the posterior oblique ligament-are the most commonly injured ligamentous structures of the knee. *The main structures of the medial aspect of the knee are the proximal and distal divisions of the superficial medial collateral ligament, the meniscofemoral and meniscotibial divisions of the deep medial collateral ligament, and the posterior oblique ligament. *Physical examination is the initial method of choice for the diagnosis of medial knee injuries through the application of a valgus load both at full knee extension and between 20 degrees and 30 degrees of knee flexion. *Because nonoperative treatment has a favorable outcome, there is a consensus that it should be the first step in the management of acute isolated grade-III injuries of the medial collateral ligament or such injuries combined with an anterior cruciate ligament tear. *If operative treatment is required, an anatomic repair or reconstruction is recommended.