Joint pain is a common complaint, often attributed to everyday strains or more familiar conditions like arthritis. However, some causes are less recognized. Pigmented Villonodular Synovitis (PVNS) is a rare disorder that can significantly affect joint health. This article clarifies what PVNS is, its symptoms, and available diagnostic and treatment approaches.
Defining Pigmented Villonodular Synovitis (PVNS)
Pigmented Villonodular Synovitis (PVNS) is a rare, benign growth affecting the synovium, the thin lining of joints and tendon sheaths. This condition involves an overgrowth and thickening of synovial tissue, forming an abnormal mass within the joint. While not cancerous, PVNS can be locally aggressive and destructive to the affected joint.
The “pigmented” aspect comes from hemosiderin, an iron-containing pigment from old blood, deposited due to recurrent bleeding into the joint. Overgrown synovial cells also show inflammation and contain macrophages and multinucleated giant cells.
PVNS most frequently affects large weight-bearing joints, with the knee being the most common site (about 80% of cases). The hip is the second most common location, but PVNS can also occur in smaller joints like the ankle, shoulder, elbow, hand, or foot. It is also known as tenosynovial giant cell tumor (TGCT).
Common Symptoms and Presentation
PVNS often presents with a range of symptoms, though onset can be gradual and mistaken for other joint issues. Common complaints include chronic, progressive joint pain and significant swelling, resulting from the overgrown synovium producing excess lubricating fluid.
Other symptoms include stiffness, limited range of motion, warmth or tenderness, and sometimes a locking, catching, or popping sensation during movement. These symptoms can fluctuate, appearing and subsiding, which can delay diagnosis.
Over time, the progressive nature of PVNS can lead to increasing joint damage. Persistent swelling and abnormal tissue growth can interfere with daily activities, making simple movements painful or difficult.
Diagnosing PVNS
Diagnosis of PVNS starts with medical history and physical examination. However, as symptoms can mimic other joint conditions, specialized imaging and tests are necessary to confirm.
X-rays are often initial imaging studies; they may show joint effusion or, in advanced cases, bone erosion. However, X-rays might appear normal in early stages without significant bone damage. Magnetic Resonance Imaging (MRI) is the most effective imaging tool for PVNS. MRI clearly shows thickened synovial lining, joint effusion, and characteristic hemosiderin deposits, which appear as low signal intensity areas.
In some cases, joint aspiration may be performed, removing fluid for analysis. Synovial fluid in PVNS cases is often bloody or dark brown due to blood products. Ultimately, a tissue biopsy of the affected synovium is the definitive diagnostic method. This sample is examined microscopically to confirm PVNS’s specific cellular characteristics.
Treatment Options for PVNS
The primary treatment for PVNS is surgical removal of affected synovial tissue, known as a synovectomy. The goal is to remove as much diseased tissue as possible to prevent recurrence and further joint damage. Two main surgical approaches are used: arthroscopic and open surgery.
Arthroscopic synovectomy is a minimally invasive technique using small incisions, a camera, and specialized instruments to remove abnormal tissue. This method is often preferred for localized PVNS due to reduced recovery time and less post-operative pain. For more extensive or diffuse PVNS, open surgery, involving a larger incision for direct joint access, may be necessary for complete removal. Sometimes, a combination of arthroscopic and open techniques is used, particularly for diffuse PVNS in larger joints like the knee, which can lead to lower recurrence rates.
In addition to surgery, adjuvant therapies may be considered for diffuse or recurrent cases. Radiation therapy, either external beam or intra-articular (injected directly into the joint), can control tissue growth or reduce recurrence risk. Newer systemic treatments, such as CSF1R inhibitors, are an emerging option for diffuse or inoperable cases, targeting specific proteins involved in disease progression. Following surgery, physical therapy is often recommended to restore joint function and mobility.
Outlook and Management
While PVNS is benign, its long-term outlook is influenced by its tendency for local recurrence. Even after surgical removal, the condition can return, with recurrence rates varying, particularly in diffuse forms. Regular follow-up appointments and imaging, such as MRI, monitor for recurrence.
The progressive nature of PVNS can lead to chronic pain and significant joint damage. In severe, long-standing cases with extensive joint destruction, total joint replacement may be necessary to alleviate pain and improve function. Despite being non-cancerous, PVNS can significantly impact quality of life due to persistent symptoms and potential joint deterioration.