Pigmented villonodular synovitis (PVNS) is a condition in which the synovium — the layer of tissue lining joints like the knee and hip — swells. Although PVNS isn’t cancer, the tumors it produces can grow to the point where they cause permanent joint damage. That’s why prompt treatment is so important.

Symptoms of PVNS like swelling, stiffness, and pain in the joint can also be signs of arthritis. Getting a correct diagnosis is essential so you can start on the right treatment.

Your doctor will begin by examining your affected joint. They might press on the joint or move it in different ways to pinpoint the exact location of your pain and listen for locking or other telltale signs of PVNS. An imaging test may help distinguish PVNS from arthritis. Doctors use the following tests to diagnose this condition:

  • X-ray
  • magnetic resonance imaging (MRI), which uses strong magnetic fields and radio waves to create pictures of your joints
  • biopsy, which involves removing a small piece of tissue from the joint to test in a lab

The main treatment for PVNS is surgery to remove the tumor and damaged parts of the joint. Sometimes the joint is replaced with a man-made prosthetic. The type of surgery you have depends on the joint involved and the size of the tumor.

Arthroscopic synovectomy

Arthroscopic synovectomy is a minimally invasive procedure to remove the tumor and the damaged part of the joint lining. You’ll typically have this surgery while under regional anesthesia, which blocks pain in the area of your body the surgeon is operating on.

The surgeon will make several small incisions in the skin. A tiny camera goes into one of the incisions. Small instruments go into the other openings.

Video from the camera is displayed on a TV monitor so your surgeon can see to perform the procedure. During arthroscopy, the surgeon will remove the tumor, along with the damaged joint lining.

Open surgery

If you have a very large tumor, your doctor may not be able to remove all of it arthroscopically. Instead, you’ll have open surgery through one large incision. An open procedure may also be best for hard-to-reach joints like the knee.

You’ll have to stay longer in the hospital after open surgery, and your rehab will take longer than it would with arthroscopic surgery. Open surgery also causes more stiffness afterward. But the risk of the tumor returning is low.

Combined open and arthroscopic surgery

If the surgeon can’t completely remove the tumor through a small incision, or the tumor is in your knee, you may have a combination of open surgery and arthroscopy.

In open surgery, the surgeon removes the tumor through the back of your knee. In arthroscopy, the joint lining from the front of your knee is removed.

Total joint replacement

After you’ve lived with PVNS for a long time, you may develop arthritis in the affected joint. Arthritis can damage the joint to the point where you have a lot of pain, and symptoms like swelling and stiffness.

Your doctor may recommend that you replace a badly damaged hip or knee joint. During joint replacement surgery, the surgeon removes the damaged cartilage and bone and replaces them with prosthetic parts made from metal, plastic, or ceramic components.

After surgery

Any surgery can cause complications like infection, blood clots, and damage to nerves. After a total joint replacement, the prosthetic joint can sometimes loosen or move out of place.

It’s possible the tumor will come back in the future, especially if your surgeon can’t remove the whole tumor. If this happens, you’ll need another surgery, or possibly several more procedures.

For the first few days after surgery, you may need to keep weight off of the joint. If it’s a weight-bearing joint like your hip or knee, you can use crutches to help get around.

Exercise is important after surgery to help you regain strength and movement in the affected joint. A physical therapist will teach you how to do these exercises correctly.

You may only need a short period of physical therapy after arthroscopy, but it could take months after open surgery.

Radiation uses high-energy rays to shrink tumors. In PVNS, it’s used together with surgery to destroy any parts of the tumor the surgeon can’t remove. You might also get radiation if you can’t have surgery, or you’d prefer not to have it.

In the past, doctors delivered radiation from a machine outside the body. Today, this treatment is often given through an injection straight into the joint. This procedure is called intra-articular radiation therapy.

Radiation can help prevent the tumor from returning, but it can also cause side effects such as:

  • skin redness
  • joint stiffness
  • poor wound healing
  • cancer in the future

A few drugs are under investigation for treating PVNS. Researchers believe PVNS may involve a change to the colony-stimulating factor 1 (CSF1) gene. This gene produces a protein that controls the actions of inflammatory white blood cells called macrophages.

In PVNS, a problem with the CSF1 gene causes the body to produce too many of these inflammatory cells, which build up in the joints and form tumors. One group of drugs blocks this process to prevent cell buildup.

These drugs include:

  • cabiralizumab
  • emactuzumab
  • imatinib mesylate (Gleevec)
  • nilotinib (Tasigna)
  • pexidartinib (Turalio)

More research is still needed to confirm the safety and effectiveness of these drugs for PVNS. Right now, they’re available in clinical trials. If surgery hasn’t worked for you, ask your doctor if you’re eligible to join one of these studies.

Which type of surgery or other treatment your doctor recommends will depend on the size of your tumor and how severely it has affected your joint. Make sure you understand all of your options, as well as the risks and possible benefits before you decide on a therapy.