Primary hydatid cyst of skeletal muscle affecting the knee: a case report.

Hydatid disease is a parasitic infection generally occurring in specific geographical areas. Exclusive involvement of the muscles is extremely uncommon, because implantation at this site would require passage through the filters of the liver and lung. We describe a patient with a mass in the popliteal fossa of the knee for 7 years who was seen for pain and was found to have hydatid disease.