Osteoid osteoma (OO) is a painful, benign bone-forming lesion, which often poses a diagnostic challenge. The aetiology of OO is still poorly understood. Although not generally accepted, an association with previous trauma or infection has occasionally been suggested. We present a case of an OO 12 years following an ulnar fracture. Radiologists should consider OO as a potential delayed "complication" of a previous fracture. Persistent pain at a previous fracture site should alert the clinician to request cross-sectional imaging. CT scanning plays a pivotal role in the correct diagnosis of OO.