A synovectomy is a surgical procedure that removes the synovium, the thin membrane lining the inside of a joint. This membrane normally produces a small amount of fluid that lubricates the joint and reduces friction. When disease causes the synovium to become chronically inflamed, thickened, or overgrown, removing it can relieve pain, reduce swelling, and preserve joint function.
Why the Synovium Becomes a Problem
In a healthy joint, the synovium is paper-thin and does its job quietly. But in conditions like rheumatoid arthritis, the immune system attacks the synovium, causing it to swell, thicken, and produce excess fluid. Over time, this inflamed tissue can erode the cartilage and bone underneath, gradually destroying the joint. Synovectomy removes that destructive tissue before the damage becomes irreversible.
Rheumatoid arthritis is the most common reason for a synovectomy, but it’s not the only one. The procedure is also used for pigmented villonodular synovitis (PVNS), a rare condition where the synovium develops abnormal growths that fill the joint with thickened, discolored tissue. Patients with PVNS often notice swelling and reduced range of motion, sometimes with locking or catching sensations that mimic a torn meniscus. Pain isn’t always a major complaint, which means people can go years before seeking treatment. Other conditions treated with synovectomy include synovial osteochondromatosis (where the lining produces loose cartilage fragments) and certain degenerative joint diseases.
When Surgery Becomes Necessary
Synovectomy is not a first-line treatment. For rheumatoid arthritis, the standard approach starts with disease-modifying drugs and biologic medications that target the underlying immune dysfunction. These medications have become highly effective, and most patients get adequate control without surgery. Synovectomy enters the picture when someone has persistent joint inflammation despite optimal drug therapy. If the synovium remains actively inflamed and swollen after months of treatment, removing it surgically can provide relief that medications alone could not achieve.
For conditions like PVNS, where the problem is a localized tissue abnormality rather than a system-wide immune disorder, synovectomy is the primary treatment rather than a backup plan.
Arthroscopic vs. Open Surgery
There are two main surgical approaches: arthroscopic and open. An arthroscopic synovectomy uses a small camera and instruments inserted through tiny incisions. An open synovectomy requires a larger incision that gives the surgeon direct access to the joint.
Each approach has a clear tradeoff. Arthroscopic surgery causes less tissue damage, leads to faster recovery, has lower complication rates, and reduces post-surgical inflammation. Open surgery, on the other hand, allows for a more thorough removal of synovial tissue, which lowers the chance of the condition coming back. For patients with advanced or widespread synovial overgrowth, an open approach may be the better choice because the surgeon can reach areas that are difficult to access through a scope.
In some cases, surgeons combine both techniques. A common strategy for complex cases involves using arthroscopy for the front of the knee and an open approach for the back, either in one session or staged as separate procedures.
Nonsurgical Alternatives
Not every synovectomy requires an operating room. Two nonsurgical options exist that destroy the synovium through injection rather than physical removal.
- Radiation synovectomy: A radioactive substance (typically yttrium-90 or phosphorus-32) is injected directly into the joint, where it damages and shrinks the inflamed synovium. It requires only a single injection, minimal pain, and no surgical recovery. Studies report effectiveness rates of 60% to 80%, with some reaching as high as 95% for pain relief at six months. The radioactive material is costly and not always easy to obtain, though safety data show no meaningful increase in lifetime cancer risk for adults.
- Chemical synovectomy: An antibiotic called rifampicin is injected into the joint to cause scarring of the synovium. One study found good results in 85% of cases treated with either chemical or radiation synovectomy, compared to 70% for surgical synovectomy. Chemical synovectomy is particularly useful in hemophilia-related joint disease, where repeated bleeding into the joint damages the synovium, and where traditional surgery carries extra bleeding risk.
Risks and Complications
Arthroscopic synovectomy carries a low overall complication rate. In a study of 200 knee procedures, the most common issues were minor: bleeding into the joint (3.5%), skin incision infection (2%), and significant post-operative pain (1.5%). More serious complications were rare. Joint infection occurred in 0.5% of cases, and rupture of the joint capsule causing leg swelling happened in 1.5%. All complications resolved with treatment and did not affect the long-term outcome of the surgery.
Joint stiffness is a concern after any joint surgery, which is why early physical therapy is important. The goal during rehabilitation is to restore full range of motion before stiffness can set in permanently.
Recovery Timeline
Recovery after arthroscopic synovectomy follows a predictable pattern. You can typically bear weight and walk on the leg shortly after surgery, though you should aim for a normal heel-to-toe walking pattern rather than limping. Long-distance walking is best avoided for the first four to six weeks.
The first six weeks focus on protecting the joint while regaining full motion and muscle strength. Physical therapy during this window is essential. At the six-week mark, if you have full range of motion, normal strength, and no swelling, you can gradually return to your previous activities. Open synovectomy generally involves a longer recovery period because the larger incision requires more healing time and creates more initial stiffness to work through.
How Well It Works Long Term
Synovectomy reliably eliminates local pain in the treated joint. For rheumatoid arthritis, the procedure provides significant relief when medications have failed, though it does not address the underlying autoimmune disease. The synovium can regrow over time, and inflammation may eventually return, particularly in systemic conditions where the immune system continues attacking joint tissue.
For localized conditions like PVNS, arthroscopic excision is effective for both localized and diffuse forms of the disease. Recurrence rates depend on how completely the abnormal tissue was removed, which is one reason open surgery is sometimes preferred for widespread cases. When recurrence does happen, repeat synovectomy or a combined approach can address the regrowth.