Pigmented Villonodular Synovitis (PVNS) is a disease in which the tissue lining the joints and tendons in the body (synovium) grows abnormally. It is characterized by a noncancerous mass or tumor. There are two types of PVNS: the local or nodular form (where the tumor involves the tendons that support the joint, or in one area of the joint) and the diffuse form (where the entire lining of the joint is involved). The most common cause of FBSS, what they sometimes forget to say, is that a small percentage of people with scar tissue experience pain. When it does cause pain that is when it’s truly called epidural fibrosis.

The exact cause of Pigmented Villonodular Synovitis (PVNS) is unknown. Some doctors believe that it is similar to arthritis, arising from swelling (inflammation) of the joint tissue. Others believe it develops like a tumor, caused by cells growing and multiplying more quickly than usual.

The average age of diagnosis for this condition is 35 years. The cause of PVNS is unknown. Treatment involves surgery to remove the tumor and damaged portions of the synovium.

The knee is most commonly affected by this condition, though it can occur in other joints such as the hip, shoulder, elbow, ankle, wrist, and rarely the jaw.