People who undergo total hip or knee replacement appear to have reduced risks of heart attack, stroke and other cardiovascular events according to a study published online recently in the journal BMJ.

“Our study suggested that in persons with moderate to severe osteoarthritis of hip or knee, joint replacement was associated with a greater than 40 percent reduction in the risk for serious cardiovascular events such as heart attack and stroke,” compared with similar patients who didn’t have surgery, says study author Bheeshma Ravi, MD, resident physician in the division of orthopaedic surgery at University of Toronto.

For the study, researchers in Ontario, Canada, looked at adults with moderate to severe hip or knee osteoarthritis. They matched 153 patients with knee or hip pain who went on to receive a joint replacement with 153 who did not, pairing people who had similar health profiles in terms of age, weight, smoking status, arthritis severity, etc. Then they looked at the rate of serious cardiac events, including heart attack, heart failure and stroke, in both groups over a period of seven years.

They found knee replacements were associated with a 54 percent reduction in heart risk, and hip replacements with a 39 percent reduction, says Dr. Ravi.

The researchers say they don’t know what caused the reduction in risk, but they speculate that the joint replacement enabled patients to increase their physical activity, which is good for the heart for many different reasons. Another factor could be less use of nonsteroidal anti-inflammatory drugs (NSAIDs), which are known to increase the risk of heart attack and stroke when taken long-term. Less stress due to pain may also play a role.

The authors acknowledge that the study has some limitations. “There is a selection bias towards offering elective surgery to healthier patients,” says Dr. Ravi.

The researchers tried to control for this bias. “We did a separate analysis where we only looked at patients that had at least one risk factor for cardiovascular events,” such as pre-existing cardiovascular disease, diabetes or hypertension, Dr. Ravi says. “We found that arthroplasty [joint replacement] still had a protective benefit, with a reduction in risk of about 30 percent.”

The findings “pass the whiff test,” says Trevor Murray, MD, an orthopaedic surgeon at Cleveland Clinic in Cleveland, Ohio. He says hip and knee replacements significantly reduce pain in people with moderate to severe arthritis – and that reduction in pain helps patients return to a more active, heart-healthy lifestyle. Dr. Murray was not involved in the study.

But, “selection bias” may exist, despite researchers’ efforts to control for it, Dr. Murray says. “Having hypertension is a heck of a lot different from having [congestive heart failure] or multi-vessel cardiovascular disease,” he notes.

And patients who choose joint replacement surgery may simply be more motivated to take care of their health. “If [patients] care enough about their musculoskeletal health to go through the pain and suffering of a total joint replacement to try to get better, they’re quite possibly the same people who are trying to walk a mile-and-a-half a day and lose weight and eat appropriately, which is really hard to capture,” says Dr. Murray. “The benefits are potentially a little bit less than the actual numbers [shown in the study].”

One thing is for certain: Joint replacement reduces pain. “Over the long run, that’s the whole point of the surgery,” says Dr. Murray.