Osteoid osteoma of the patella: a case report.

Though osteoid osteoma is a common primary benign lesion of the bones, intra-articular involvement is rare and poses diagnostic difficulties when it affects middle-aged patients. We present the case of a 51-year-old woman with a 2.5 year history of anterior knee pain that was misdiagnosed as osteochondritis dissecans.

Echinococcal synovitis of the knee joint.

Bone lesions are present in 1% to 2% of cases of hydatid disease. Hydatid synovitis can usually be identified due to secondary extension from the adjacent bone, or infrequently after hematogenous spread. We present an extremely rare case of hydatid synovitis without bony involvement.