Cystic Echinococcus in the bone is rare, comprising 0.5% to 2.5% of all human hydatidosis Association of Hydatid disease to pathologic fractures involving knee prosthesis have not yet been described A combined surgical and medical approach is of paramount importance to avoid recurrence Resulting osseus defects is challenging and require specific prosthesis when treating this entity.

Hydatid disease in humans caused by the parasitic tapeworm Echinococcus granulosus has an osseous involvement of about 0.5% to 2.5% of all cases in humans. The location of hydatid cysts in the tibia is seldom described in the medical literature, and its diagnosis and treatment is challenging.

This paper presents a patient, with a long term, well tolerated, bilateral total knee arthroplasty (TKA), treated at our clinic, with a recent history of pain and oedema in her left upper leg. After achieving a, radiologically and histopathologically, well documented, diagnosis of Echinococcosis lesion in her left proximal tibia, a surgical intervention was planed, a wide resection of the cyst performed, and a specific anti-helmintic therapy was instituted. Four years later the patient returns to the investigators observation complaining of pain and unable to bear weight on her left knee, from which a pathologic fracture, adjacent to the tibial component was diagnosed.

After surgical debridement of the newly advanced hydatid cyst growth, the TKA was revised, and due to the tibial component failure and the femoral implant loosening, a semi-constrained total knee revision arthroplasty was executed. Functional outcome was excellent.

Although challenges in treatment of musculoskeletal hydatid cysts (HC) lesions have been documented, data regarding the musculoskeletal HC lesions resembling tumor is scarce, and those resulting in a prosthetic failure haven't been published. The authors intend to add data concerning the therapeutic approach to this entity.

Inclusion criteria

• Patients with echinococcus infection
• Patients which this infection compromises knee stability.

Exclusion criteria

• bacterial infection
• immunocompromised patients

No personal patient information is to be made available.