For patients who have had an acute onset of pain, radiographs should be obtained to rule out an avulsion fracture of the tibial tubercle. Ultrasound and MRI scans can confirm the diagnosis of OSD, but are generally unnecessary. SLJ disease and patellofemoral syndrome occasionally coexist with OSD in adolescents. SLJ disease involves pain, swelling, and tenderness of the inferior patellar pole at the origin of the patellar tendon. Unlike the more obvious OSD, this diagnosis will be missed unless the examiner palpates the inferior patellar pole with the patient's knee extended and the patellar tendon relaxed.
Radiographs are usually normal but can show calcification or an elongated inferior patellar pole.
Patellofemoral syndrome probably arises from repetitive stress of the patella on the femur, but the exact etiology is unknown. Patients present with a history of chronic activity-related anterior knee pain that vaguely localizes to the peripatellar area. With the knee in this position the patella begins to contact the trochlear groove of the femur. Osteochondritis dissecans is a rare but serious cause of adolescent knee pain involving an abnormality of the articular cartilage and the underlying bone. Patients present with diffuse knee pain, and can have loss of motion and a knee effusion.