OSD is thought to be caused by repetitive strain and chronic avulsion of the secondary ossification center of the tibial tuberosity, i.e., by small injuries due to repeated overuse before the area has finished growing. The repetitive strain is from the strong pull of the quadriceps muscle produced during sporting activities, particularly during running, jumping and climbing. Accordingly, OSD is common in adolescents who play soccer, basketball and volleyball, and who participate in gymnastics. The tibial tuberosity avulsion continues to grow, ossify and enlarge. The intervening area may become fibrous, creating a localized nonunion, or may show complete bony union with mild enlargement of the tibial tuberosity. In any case, the result is a traction apophysitis of the tibial tubercle.
Diagnosis is based on the clinical features of the disease and on diagnostic imaging. Particularly in unilateral cases of OSD plain radiographs of the knee are recommended to rule out other conditions such as acute tibial apophyseal fracture, infection, or tumor.
The treatment of OSD should start with conservative treatment modalities including rest, icing, modification of activities, and rehabilitation exercises. Patients not responding to conservative treatment for six months (approximately 10% of all patients) should then be subjected to radial shock wave therapy (RSWT). Surgery should be considered for recalcitrant cases of OSD in skeletally mature patients, aiming at surgical excision of the ossicle (in case of a localized nonunion) and/or free cartilaginous material.