A 29-Year-Old Man With Buttock Pain

A 29-year-old man presented with a 2-month history of nonradiating pain in the left buttock and lateral hip. There was no known history of trauma. The patient complained of pain at all times, with exacerbation with any weightbearing activity. The pain had progressed such that at the time of presentation, the patient was no longer able to maintain his occupation as a manual laborer. He denied any constitutional symptoms. Physical examination revealed no palpable masses or areas of tenderness. The ROM of the ipsilateral hip was full, on passive and active examination. However, this ROM resulted in pain in the buttock. Strength in the involved extremity was 5/5 on manual muscle testing. Straight leg raise testing, on the ipsilateral and contralateral sides, was not provocative. Laboratory studies, including complete blood count, serum chemistries, prostate specific antigen, serum immunoelectrophoresis, and erythrocyte sedimentation rate all were within normal limits. Plain radiographs, CT scans, and MRI scans were obtained (Figs 1–3). Based on the history, physical examination, laboratory studies, and imaging studies, what is the differential diagnosis? Orthopaedic • Radiology • Pathology Conference