Epiphyseal osteochondroma of the anterior cruciate ligament.

An 8-year-old Black boy complained of pain, swelling, and a decreased range of motion in the knee. One arthrotomy operation was reported to show a normal knee joint. Six months later, a second arthrotomy demonstrated an osteochondroma growing from the epiphysis into the anterior cruciate ligament. Epiphyseal osteochondroma should be added to the working differential diagnosis on children with effusion and decrease of knee motion.