Osteoid osteoma is a relatively common benign tumor that most commonly affect the cortex of the long bone, Adolescent and young adult males are most frequently affected. It causes aching pain that worsens at night and commonly is relieved by aspirin. The typical radiographic appearance is a lucent nidus with surrounding dense cortical thickening. If the lesion is located in intra-articular cancellous bone, an osteoid osteoma may present with clinical findings that are more indicative of an inflammatory synovitis, and with atypical radiographic findings such as lack of both surrounding sclerosis and a lucent nidus. Therefore intra-articular osteoid osteoma may pose a diagnostic difficulty. Recently, we experienced 3 cases of intra-articular osteoid osteoma(2 humeral haed, 1 femoral head) and present them in detail.