Deformation of the patellofemoral joint caused by synovial hemangioma

A 15-year-old girl with synovial hemangioma of the knee joint presented with gait pain and occasional sudden swelling for over 7 years. Plain radiographs showed an irregular joint line and a lateral shift of the patella caused by malformation of the patellar groove. Arthroscopy was performed to resect the tumor and to release the lateral patellar retinaculum. If the synovial hemangioma exists in the patellofemoral joint during the growth period, we propose that early surgical treatment is necessary to avoid the deformation of the joint.