Osteochondral lesion of the fifth metatarsal head in a triathlete.

Osteochondral lesions (OCLs) are rare joint disorders, typically found in the larger joints of the body and less so in smaller joints (J Bone Joint Surg Am 41-A:988-1020, 1959; Arthroscopy 6(3):190-197, 1990; Clin Orthop Relat Res 148:245-253, 1980). Although their specific cause is subject to frequent debate, they are often caused by trauma with subsequent compromise of the articular cartilage (Arthroscopy 6(3):190-197, 1990; J Bone Joint Surg Am 78(3):439-456, 1996). Symptoms are typically attributable to a mechanical defect, either of the bony defect or a flap of cartilage. The current case report describes an osteochondral lesion of the head of the fifth metatarsal which is a heretofore unreported location. Magnetic resonance imaging (MRI) of the lesion revealed a notable subchondral bone signal change, indicating a possible synovial fluid pressure phenomenon rather than a mechanical defect.