Journal of Research in Medical Sciences1735-1995101200501284044ENDep. of Orthopedics, Isfahan University of Medical SciencesDep. of Orthopedics, Isfahan University of Medical SciencesDep. of Orthopedics, Isfahan University of Medical Sciences2006082820060828Although osteoid osteoma is a relatively common lesion, it rarely occurs at elbow. We report two cases of osteoid osteoma of elbow in trochlea. Diagnosis was delayed because of non-specific clinical and radiological features. The two patients suffered from flexion contracture of elbow due to synovitis, while at the same time, pronation and supination remained normal. Only one of the patients complained of specific nocturnal pain. Both patients had latencies between the onset of symptoms and the appearance of radiological signs. Open surgical excision of the nidus resulted in complete relief and motion recovery in both cases. Diagnostic difficulties and treatment options are discussed below. Key words: Osteoid osteoma, Elbow, Trochleahttp://jrms.mui.ac.ir/index.php/jrms/article/view/395http://jrms.mui.ac.ir/index.php/jrms/article/download/395/138