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. A 74-year-old man with diagnosed hydatid disease was admitted to our department because of left knee swelling. Neither physical examination nor laboratory studies revealed any remarkable findings. Radiographic evaluation of the knee joint was noncontributory. The patient underwent an arthroscopically assisted synovectomy, and the biopsy revealed an echinococcus contamination. No complications occurred during the postoperative period.