An Unusual Cause of Knee Mass: Osseous Hydatidosis.

Hydatid disease (hydatidosis) is a zoonotic infection caused by the larval stage of the parasitic tapeworm Echinococcus granulosus endemic in some sheep-raising areas. The liver and lungs are most commonly affected. Bone involvement (osseous hydatidosis) is distinctly uncommon, and its diagnosis and treatment can be challenging. We report a case of a 54-year-old male with right knee pain and edema and an extensive lesion on the femur; he was diagnosed with knee hydatidosis and was successfully treated with surgery and albendazole. This case reinforces the importance of the rare osseous hydatidosis as part of the differential diagnosis of bone lesions.