There are many causes of knee pain in the athlete. Clearly, common things, such as meniscal tears, ligament sprains, contusions, and patellofemoral dysfunction, are common. The infrequency of other entities, however, should not make the physician complacent. A thorough history and physical examination will, in most cases, elicit inconsistencies in the occasional athlete presenting with one of these uncommon causes of knee pain (Table 1). Diagnosing these uncommon causes, when they do present to the health care provider, allows for early and correct treatment with a more rapid return to sports.