Pannus and Rheumatoid Arthritis (RA): The Basics

Medically Reviewed by Melinda Ratini, MS, DO on June 07, 2022
4 min read

Pannus is a type of extra growth in your joints that can cause pain, swelling, and damage to your bones, cartilage, and other tissue. It most often results from rheumatoid arthritis, an inflammatory disease that affects your joints, though other inflammatory diseases are also sometimes to blame. In the past few years, advances in RA treatment have made pannus far less likely than it has been in the past.

A delicate membrane called the synovium lines each joint in your body. It connects to cartilage, the soft, spongy material at the ends of your bones that helps protect them.

In a healthy joint, the synovium lubricates the joint, supplies nutrients, and even helps make building materials like collagen. But in some people with RA, it can start to grow too much.

This extra synovial tissue can thicken and grow into areas that it shouldn’t. Special immune system cells (T and B lymphocytes, macrophages, mast cells, and others) make up much of these new clumps of tissue. Your doctor might call them pannus formations.

This type of growth (your doctor might call it synovial hypertrophy) can cause stiff joints. If it goes on too long, it can damage bone, cartilage, and other tissue.

In some ways these growths seem to act like a tumor. But pannus isn’t cancer and can’t spread to other areas of the body.

Rheumatoid arthritis causes the extra tissue growth (pannus) in your joints. Serious pannus formations develop only if you don’t get treatment for RA or if your doctor can’t find a way to treat it effectively. This is rare.

But what causes rheumatoid arthritis?

Scientists know it happens when your immune system starts to misfire and attack your joints, but they don’t yet know why this happens in the first place.

Your genes seem to play a role, but just because you have the genes that make RA more likely doesn’t mean you’ll get the disease. Certain things in the environment -- smoking, for example -- also can lead to RA. But not everyone who smokes or lives around smokers gets RA, either. And some people get RA without the genes or any known environmental factors.

Scientists continue to study the roots of this autoimmune disease.

The symptoms are a lot like those of rheumatoid arthritis itself: pain, swelling, stiffness, and tenderness in a joint, often on both sides of your body (both knees, both wrists, both thumbs, etc.).

With pannus formations, the pain can be severe. The swelling can be bad enough that the joint looks misshapen, even to the average person.

But if you get regular checkups for your RA, you’re unlikely to ever get the pannus formations that can damage your joints. This is largely due to recent advances in the early diagnosis and treatment of rheumatoid arthritis.

Your doctor will typically diagnose you with RA before pannus can even start and long before it could cause any obvious harm. But if you’ve had RA for a long time and your medication hasn’t kept the disease in check, you could get pannus formations.

To know for sure if the joint is just swollen or if it’s really damaged or deformed, the doctor will do imaging tests like X-rays, an MRI, or a CT scan. These pictures can show the pannus formations and whether they’re large enough to eat away bone and cartilage or otherwise damage the joint.

Your doctor will treat pannus largely the same way they would rheumatoid arthritis.

Because pannus is a sign of more serious, long-standing RA, your doctor might skip first-line treatments with over-the-counter non-steroidal anti-inflammatory drugs like ibuprofen and naproxen and start you on prescription meds. What you take will depend on your symptoms, your previous treatments, and how long you’ve had RA:

It can take 3 months or longer before you see improvement with DMARDs or biologics. But they can be very effective. Often they completely reverse the growth of pannus formations. But in more serious cases, where the formations have damaged bone or cartilage, it isn’t usually possible to repair the damage with medication.

If your pannus doesn’t reverse, or continues to grow, surgery may be an option. The doctor can remove extra tissue in the joint to ease your symptoms and make the joint work better.

This depends in part on your lifestyle and on the location of the formation in your body. Talk to your doctor about the best approach for you.