What Is (PVNS) Pigmented Villonodular Synovitis?

Medically Reviewed by Tyler Wheeler, MD on February 25, 2024
4 min read

Pigmented Villonodular Synovitis (PVNS) is a rare condition that causes painful swelling in certain joints. It can cause large, noncancerous tumors to form at these joints. Estimates show that around four or five people out of every 10,000 will have this condition, which is commonly diagnosed between ages 30 and 50.

Usually, PVNS is found in only one joint. In 80% of cases, this will be one of the knee joints. It can also affect your hips, shoulders, elbows, ankles, hands, feet, and—most rarely—your jaw. 

PVNS can be very painful and can interfere with your daily life. In most cases, surgery is required to help relieve your symptoms.

The exact cause of PVNS is unknown.

In a normal joint, the synovium is a thin layer of tissue that surrounds all of your joints and tendons—the connective tissues between muscles and bones. When healthy, the synovium produces a small amount of fluid that helps with movement by lubricating your joints. 

When you have pigmented villonodular synovitis, your synovium starts to thicken and the cells divide—producing more cells—more than they should. It also produces too much lubricating fluid, which causes painful swelling. 

There are two main types of PVNS: 

  • Localized PVNS. In this form, only certain parts of your joint are affected. This is also the kind you have when your tendon is affected. 
  • Diffuse PVNS. In this form, the entire joint shows symptoms. This kind is rarer, more painful, and harder to treat than localized PVNS. 

PVNS symptoms are much more severe in the diffuse version of the condition.

PVNS is progressive, so symptoms will slowly become worse over time. The symptoms also come and go. You won’t need to deal with all of them all of the time.

PVNS symptoms include: 

  • Significant swelling at the joint
  • Joint pain. Up to 99% of patients with PVNS have joint pain. 
  • Heat and tenderness at and near the joint
  • Limited movement of the joint
  • Locking or catching of the joint
  • Popping of the joint
  • Hemarthrosis. Blood collects in the joint even when you haven’t damaged it. 

If PVNS is left untreated for a long time it will cause more and more damage to the joint. Eventually, it will start to damage your bones and the tendons that are attached to them.

Most cases of PVNS are diagnosed using magnetic resonance imaging (MRI). The swelling and growth at the joint are visible when doctors use this technique. 

Researchers have also found a few suggestive links to PVNS that could be used to diagnose the condition in the future. These possible causes include:  

  • Genetic changes. Researchers have noted that certain changes happen in the genome of people with PVNS. So far, though, they don’t understand a causal link between the condition and these changes. 
  • Proteins. When you have PVNS, a small number of cells within the synovium start to produce a protein that they shouldn’t. This protein is called CSF-1R. Researchers know that this protein is somehow related to the condition, but they don’t clearly understand why. 
  • Prior injury. There is also some evidence that PVNS develops in joints that have been damaged in previous injuries. 

If you have PVNS, you’ll need surgery to relieve the symptoms and prevent further damage to your joint. If your tendon has already been damaged, your surgeon will repair that during surgery, too.

Types of surgery include: 

  • Arthroscopic surgery. This is a type of surgery where your surgeon will make small incisions around the joint. A small camera will be inserted through these incisions. It is used as a guide while the surgeon cuts away and removes all of the affected parts of the synovium. This is the most common surgery for localized PVNS. 
  • Open surgery. For this surgery, one large cut is made so your surgeon can reach the entire joint. This is best when you have diffuse PVNS, because the surgeon will need to take the entire lining and tumor out of the joint. 
  • Combination surgery. This is most often used when you have localized PVNS at the back of your knee joint. The back will have a large cut for open surgery, but the front will be treated arthroscopically to prevent the stress on your joint that a full open surgery causes. 
  • Total joint replacement. If you have late-stage PVNS, you may need a new joint, which is made of metal or plastic.

After these surgeries, localized PVNS rarely comes back.
However, diffuse PVNS recurs in 10% to 30% of all people with the condition. You’ll need to schedule follow-up appointments with your doctor to make sure that the condition hasn’t returned. If it does, they may recommend an alternative form of treatment, including: 

  • Radiation. This is used to shrink tumors, including the non-cancerous kind that PVNS creates. There are a few ways to administer radiation. The newest is intra-articular radiation, where radioactive fluid is injected straight into your joint. Radioactive fluid gives off very high-energy particles at random times. 
  • Drug therapy. There is currently only one drug that’s FDA approved to treat PVNS. It’s designed to target the protein CSF-1R. There are currently nine clinical trials that are ongoing or have just finished. Their goal is to develop new drugs for this condition. Your doctor will know if you’re eligible for any of these drug trials. 

Talk to your doctor when you have recurring or intense joint swelling and pain.