Pigmented Villonodular Synovitis

Recently a friend was diagnosed with PVNS as a cause of knee pain. It's a fascinating disease. I have compiled and plagerized some of my readings. References at the end.

• Epidemiology: Uncommon but not necessarily rare (1.8 cases per 1 million people per year). Affects synovial lined joints, bursae, and tendon sheaths. The knee is the most commonly affected joint, followed by the hip, ankle, small joints of the hands and feet, shoulder and elbow. more often in patients aged 20-50 years the knee (approximately 80%),usually is monoarticular. localized form occurs most frequently in the fingers—in particular, in the volar aspect of the first 3 fingers. It is the most common soft-tissue tumor of the hand.
  

• Etiology controversial, several theories based on histology (Localized lipid metabolic derangement, Repeated nontraumatic inflammation, A benign neoplastic process, A response to blood or blood products within the joint)
  

  "For unknown reasons, some or all of the synovial lining tissue of a joint occasionally undergoes a change and becomes diseased, wherein the joint lining tissue becomes thick and overgrown and accumulates a rust-colored, iron pigment known as hemosiderin. Strange, foamy cells and large (so-called "giant") cells with many nuclei also appear. The overgrowth of the joint lining tissue can occur diffusely throughout a joint by way of a generalized thickening of the entire lining membrane, or a localized area of synovial membrane can overgrow and form a discrete nodule (tissue mass) that remains attached to the rest of the internal joint lining by way of a stalk."ref

• 2 forms:
  
• Diffuse joint involvement: affects the entire synovial lining of a (typically involves the large joints) joint, bursa, or tendon sheath,
  
• The rare localized form of the disease usually has a female predominance and presents as a pain-free, slowly enlarging mass most frequently occurring on the flexor aspect of the fingers. rare focal localized form typically occurs around the small joints of the hands and feet. Often appears around tendon sheaths, in which case it is termed giant cell tumor of the tendon sheath. Rarely, the localized form may develop around large joints. (The term PVNS is used when the condition, in either diffuse or localized form, affects a joint.)
  

• History: insidious onset, slow progression, nonspecific presentation (Intermittent swelling and stiffness, diffuse discomfort rather than severe focal pain, usually not preceded by trauma, occasionally a "popping" sensation). The swelling is disproportionate to the degree of pain. Acute pain may occur with nodular torsion and/or infarction. Most common incorrect working diagnoses were patellofemoral syndrome and meniscal lesion (also inflammatory arthritis, ligament instability).

• Exam: 96% have distention of the suprapatellar pouch and a large warm tender effusion. 40% have a diffuse palpable synovial mass, one or more palpable nodules. Slightly decreased ability to flex and extend the joint. mild to moderate tenderness, mainly over the medial patellofemoral area. Arthrocentesis usually yields blood-tinged synovial fluid without preceding traum.


• Imaging: plays an important role in the diagnosis, treatment, and follow-up monitoring of the disorder.

• Xray is often normal and can not determine the extent of disease.
  
• may see effusion (Occasionally dense from hemosiderin).
• may see periarticular soft tissue density
• expansion of the suprapatellar pouch and patellofemoral osseous changes (abnormal tracking as synovial mass lifts/stretches extensor mech)
• sometimes osteopenia and secondary degenerative changes may occur later (concentric cartilage space narrowing, subchondral cyst, and osteophyte formation)
• Calcifications are NOT a usual feature. Rarely, foci of dystrophic calcification. Differentiating calcifications from hemosiderin-laden foci may be difficult on MRI, XRAY should be used in this setting to confirm or deny.
  
• Well-corticated pressure erosions (saucerization) and cysts may occur on either side or both sides of the joint.
• Nodular form most commonly results in localized swelling of the palmar aspect of a finger.
  
• Arthrography demonstrates multiple, irregular, nodular filling defects of variable sizes. These produce the typical cobblestone appearance of the synovium.
  
• bone scan is not very helpful. Hypervascularity and areas of erosion may result in increased radionuclide uptake. Soft-tissue masses often demonstrate increased uptake on blood-pool images.
• CT does not completely show extent of disease and other pathology around or within the joint. Useful for needle biopsy guidance and for preoperative planning. Findings invariably are diagnostic:
• lesions appear hyperdense due to the presence hemosiderin,
  
• valuable in delineating bone cysts and erosions.
• Affected synovium is hypervascular and generally enhances following administration of radiographic contrast.
  
• MRI is imaging modality of choice in the evaluation of synovial and soft-tissue lesions. Variable appearance, depending on relative composition proportions of hemosiderin, lipid, fibrous tissue, cyst formation, and cellular elements. MRI findings are diagnostic >95% of patients. Rarely, confused with synovial osteochondromatosis (xrays can help). MRI findings:
• nodular intra-articular masses Low signal intensity (T1-, T2-, and proton density) due to hemosiderin deposits within the affected tissue and is accentuated on T2.
• lipid-laden macrophages, resulting in focal regions of high T1 and intermediate T2.
• Hyperplastic and hypervascular synovium enhances with gadolinium.
• Bony erosions (when present) and extra-articular extension of the lesion are well demonstrated on MRI.

• 

• Differential Diagnosis: Osteoarthritis, Inflammatory arthritis, Rheumatoid arthritis, Psoriatic arthritis, tuberculosis, hemophilic arthropathy, synovial hemangioma, amyloid arthropathy, Systemic lupus erythematosus, Septic arthritis, Synovial chondromatosis, Pigmented villonodular synovitis, Benign or malignant bone tumor
• Definitive Diagnosis: synovial biopsy

• Pathology: Grossly, large effusions, bony erosions, proliferative hyperplastic synovium with brownish villonodular fronds. Two types of villi are present in the diffuse form of PVNS, including coarse villi with a "shag carpet" appearance, and fine or fernlike villi. The nodular component is seen predominantly in tendinous or extra-articular lesions. The nodules are well demarcated and may be sessile or pedunculated, although they lack a true capsule. Histologically, mononuclear/histiocytic infiltrate in fibrous stroma of synovial membrane Hemosiderin-laden macrophages give the characteristic brown color; also lipid-laden foam cells and multinucleated giant cells. Hemosiderin lends the tissue a characteristic pigmented appearance. The lesions tend to be hypervascular and demonstrate synovial hyperplasia.

• Treatment: Synovectomy. Curettage/bone grafting as necessary.. high rate of local recurrence. Synovectomy may not relieve all symptoms in patients with significant destructive changes in the joint. In these situations, arthrodesis or total joint replacement should be considered. Radiotherapy can be considered in patients with previous adequate resection of disease who experience local relapse and in patients with a large amount of disease in whom complete resection is not possible.(13 of 14 were disease-free at a mean follow-up period of 69 months).
  

"Clinicians should always keep in mind the possibility of PVNS when presented with a patient who is suffering from unexplained, recurrent fluid accumulations in one of their joints, especially when the joint fluid has a slightly more orange-brown color to it than normal." ref

References:

1. Emedicine
2. AAFP
3. Kneeandshoulder
4. Interesting patient experiences