UCLA Radiological Sciences Proceedings

Osteoid osteoma is a benign bone-forming tumor with characteristic clinical and imaging features. Clinically, patients present with pain at the site of the tumor, worsening at night and relieved by nonsteroidal anti-inflammatory drugs. The typical imaging features of osteoid osteoma include a round or oval intracortical radiolucent lesion with surrounding cortical thickening and reactive sclerosis. However, intra-articular osteoid osteoma often has imaging and clinical features that deviate from those of osteoid osteoma, which may result in delayed diagnosis. We report a case of intra-articular osteoid osteoma in a 20-year-old woman with a history of ankle pain. The variant clinical and imaging characteristics of intra-articular osteoid osteoma and the important considerations for the treatment of patients with this condition are briefly discussed.