Osteoid osteoma of the lateral talar process presenting as a chronic sprained ankle.

Pathologic conditions of the lateral talar process may be difficult to diagnose using physical examination and roentgenographs. A computed tomography scan of the hindfoot is often useful to define lesions of the lateral process. We report a case of osteoid osteoma of the lateral talar process that defied diagnosis for 4 years. The patient had an antecedent history of an inversion injury, which had been treated as a chronically painful sprained ankle without resolution of symptoms. The tumor was ultimately identified on a computed tomography scan, best seen on a coronal section through the talus. The patient had complete relief of pain after excisional biopsy of the tumor.