Pigmented Villonodular Synovitis (PVNS) affecting the Knee

Introduction

Pigmented Villonodular Synovitis (PVNS) is a rare condition where the lining of a joint, called the synovium, becomes thickened and overgrows. This abnormal synovial tissue can also form small nodules or masses inside the joint. The knee is the most common joint affected by PVNS.

Symptoms of PVNS Affecting the Knee Joint

When pigmented villonodular synovitis occurs in the knee, it often causes pain, swelling, and stiffness. Some people may also notice the knee feels unstable or locks during movement, especially if the excess tissue gets caught between the bones. Over time, PVNS in the knee can act much like arthritis. The thickened tissue and nodules can damage the smooth cartilage that covers the joint surfaces, leading to increased wear and tear. This may cause ongoing swelling, aching, or a feeling of fullness in the knee. In more advanced cases, the damage can limit mobility and make everyday activities like walking or climbing stairs difficult. Left untreated, PVNS can cause significant joint damage and even permanent arthritis. To learn more about PVNS click here.

How is PVNS of the Knee Joint Diagnosed?

To diagnose pigmented villonodular synovitis in the knee, a doctor will start by asking about symptoms such as pain, swelling, or episodes of locking. During a physical exam, they may notice fluid in the knee or limited range of motion. Imaging studies are often needed to confirm the diagnosis. X-rays may show signs of joint damage, while an MRI scan is particularly useful for detecting thickened synovium and nodules. Sometimes, a sample of the tissue (biopsy) is taken to confirm the diagnosis under a microscope.

Treatment of PVNS of the Knee Joint

Treatment for PVNS in the knee usually involves surgery. The main goal is to remove the abnormal synovial tissue to reduce pain, improve movement, and prevent further joint damage. This can be done through minimally invasive arthroscopic surgery or, in more extensive cases, open surgery. If the condition has already caused significant arthritis, a joint replacement may be considered. The prognosis after treatment is generally good. However, PVNS has a tendency to return, so follow-up with a doctor is important. With proper care, many patients regain good knee function and relief from their symptoms.

Edited by Stephen Pinney MD, September 19th 2025.