Injuries to the medial side of the knee are not always isolated injuries of the superficial medial collateral ligament. Medial-sided injuries can also involve the deep medial collateral ligament, the posteromedial corner, or the medial meniscus. Magnetic resonance imaging is a useful adjunct to the physical examination; however, the extent of medial-sided injuries is frequently underappreciated on these images. An understanding of the anatomy and biomechanics of the medial side of the knee and a thorough physical examination aids the physician in determining the full extent of injury and helping the physician to treat each unique injury pattern.