Those who have surgery to repair a torn anterior cruciate ligament, or ACL, may be able to stave off knee osteoarthritis by restoring full range of motion to the joint, according to a study published in 2011 in  The American Journal of Sports Medicine

The ACL is the knee ligament that connects bones in the thigh and shin and helps the knee stay stable. Doctors have long known that certain knee injuries, such as an ACL tear, can predispose an individual to getting knee osteoarthritis, or OA. One study, published in in 2005 in the journal Arthritis & Rheumatism found that nearly one in four knee OA patients once had an ACL tear.

ACL tears are treated by reconstructive surgery and rehabilitation, or sometimes by rehabilitation alone. The study suggests rehab should not be stopped before full range of motion is restored to the joint.

“Many times [after ACL surgery and rehabilitation], people don’t have full range of motion in their knees, but they’re stable and doctors say, ‘That’s OK.’ But 10 years later, some of those people have arthritis damage,” says orthopedic surgeon K. Donald Shelbourne, MD, who conducted the study at his clinic, the Shelbourne Knee Center in Indianapolis.

Dr. Shelbourne’s study followed 780 patients for a minimum of five years after ACL reconstruction. He and his research team used X-rays and range-of-motion tests to evaluate the patients at regular intervals. They found that 71 percent of the patients with normal range of motion also had normal X-rays at the end of the study period, showing no evidence of arthritis in their knee. By contrast, only 55 percent of patients with reduced range of motion had X-rays that showed no evidence of OA.

“People who had normal motion had much better X-rays [without indications of arthritis] than people who didn’t have normal motion,” explains Dr. Shelbourne.

So, does early arthritis stop range of motion or does maintaining range of motion help prevent arthritis? Dr. Shelbourne says it could be a little bit of both. He says the message for patients is: Stick with rehab following ACL surgery until you have equal range of motion in both knees.

Jonathan Chang, MD, a clinical associate professor of orthopaedics and sports medicine at the University of Southern California in Alhambra, finds the new research promising and hopes further studies will continue to build on it.

“One of the devastating complications of having an ACL tear is getting early arthritis. To date, we have not been able to accurately identify who is at risk. That’s why this is important. It’s another piece of the puzzle to help us figure out who is at risk,” Dr. Chang says.

But he also says that while sports doctors are excited to see this data indicating the benefits of extended rehabilitation, it may be a challenge for patients to get insurance companies to cover it. “While doctors might be able to identify that [patients] need more rehabilitation because they haven’t achieved the goals, oftentimes insurance companies will cut them off,” Dr. Chang explains.