Imaging the ligaments of the knee.

The knee is a complex joint capable of six types of motion, stabilized by four major ligaments and a capsule, and prone to soft tissue injury in our active society. Because of the complexity of motion and combination of ligamentous restraint, clinical evaluation is often difficult, particularly in the setting of an acute injury where pain and presence of an effusion limit the physical examination. Plain radiography is occasionally helpful in evaluation of the initial injury and quite useful in follow-up evaluation of ligament reconstructions and repairs. Magnetic resonance imaging (MRI) has become increasingly important in evaluation of both knee injury and subsequent reconstructions and repairs. This article will review knee anatomy, touch on important elements of the history and physical examination, and discuss plain film and MRI evaluation of both knee injury and reconstruction/repair for each individual ligament.