Sinding-Larsen-Johansson syndrome is similar in etiology to Osgood-Schlatter disease in that it is the result of repetitive microtrauma. However, in this condition the stress is directed at the attachment of the patellar tendon on the inferior pole of the patella. Traction tendonitis, Sinding-Larsen-Johansson syndrome results in calcification or ossification of the patellar tendon and can often be demonstrated at plain radiography.