Pigmented villonodular synovitis of knee diagnosis
PVNS presents with acute episodic attacks of pain and swelling. Patients may have mechanical symptoms (locking and catching). When synovial fluid is aspirated from the joint, it is hemorrhagic and dark brown. A biopsy is diagnostic. The differential diagnosis is primarily to separate PVNS from rheumatoid arthritis. Unlike PVNS, RA tends to affect multiple joints and be symmetric.
PVNS usually presents as a monoarticular hemarthrosis, and may exist in a nodular or a diffuse form. The diffuse form is either active or inactive. A diffuse mass may be present on exam. Erosions are seen on x-ray. The nodular form is less common and is not as destructive as the diffuse form of PVNS. It may cause recurrent hemarthrosis and the aspirate may be of normal color ( does not show classic brown color).
MRI Findings can help tremendously with diagnosis. The most characteristic feature of PVNS on MRI is the presence of intraarticular nodular masses of low signal intensity on T1,
T2-weighted, and proton-density-weighted images. Diseased synovium and focal masses may be best demonstrated on T2 images, showing up as an area of absent signal intensity. This phenomenon is due to hemosiderin deposition Other conditions to consider are hemophilic arthropathy, soft-tissue sarcoma, fibromatosis, synovial chondromatosis, septic arthritis, nflammatory arthritis, and hemorrhagic synovitis.
Under the microscope, PVNS shows subsynovial nodular proliferation of large round, polyhedral, or spindle cells with prominent cytoplasm and pale nuclei. Phagocytic histiocyte-like cells are also present as are lipid-laden foam cells and multinucleated giant cells that are interspersed with hemosiderin-laden cells.
Giant cells appear to have a phagocytic role.
Treatment is usually arthroscopic synovectomy. This is indicated for the nodular form or for the inactive form of diffuse disease. The posterior compartment needs to have the synovium removed. Some authors advocate the use of low dose radiation therapy following arthroscopic synovectomy. The combination therapy was effective in reducing symptoms of pain and edema, and in improving overall function of patients. Open synovectomy is the treatment of choice for patients with the active form of diffuse disease. The recurrence rate is relatively high and therefore both anterior and posterior open synovectomy is required. Total knee replacement is indicated for PVNS with joint destructive changes.
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