A 65-year-old woman presented with an 18-month history of an enlarging soft-tissue mass of the right lateral knee. She had undergone a cemented total knee arthroplasty of the same knee 8 years previously. The mass was restricting the range of motion but the knee was not painful. Plain anteroposterior and lateral radiographs (Fig. 1) demonstrated a large soft-tissue mass laterally at the knee joint with an associated pe- riosteal reaction in the distal femur and proximal tibia. Magnetic resonance imaging (Fig. 2) showed a heterogeneous mass laterally and a second mass on the medial tibial side of the joint. Open biopsy was undertaken and the specimen was reported as comprising a fibrinous exudate with no evidence of malignant disease (Fig. 3).
The development of a soft-tissue mass in response to wear debris after total joint arthroplasty is a well-recognized complication. Although the risk of a sarcoma developing at the site of a total joint replacement is small, a definitive diagnosis must be made before proceeding with revision surgery. n
Footnotes
Section Editor: Robert S. Bell, MD
Submissions to Surgical Images, musculoskeletal section, should be sent to Dr. Robert S. Bell, University Musculoskeletal Oncology Unit, Ste. 476, 600 University Ave., Toronto ON M5G 1X5; fax 416 586-8397.