Dr. Dragoo says he does see one shortcoming with this study and that’s the fact that patients were only assessed after seven-and-a-half years.

“It’s medium-term follow-up. But what we really need to do is show at 15 or 20 years, these implants are failing at the same rate, high impact or not. We need additional reports before we can come to the overall conclusion that this higher impact activity is safe,” Dr. Dragoo says. “But intermediate follow-up lends credence to the idea that more activity is OK for implants. It’s worthwhile reporting even though it doesn’t conclusively prove they are safe.”

Bashir A. Zikria, MD, an assistant professor in the Department of Orthopaedics at Johns Hopkins University Medical Center who specializes in sports medicine also has concern about how long these study participants were followed. “It’s only seven-and-a-half years. The thing you worry the most about is long-term. As far as wear, you don’t know wear analysis for at least 10 years,” Dr. Zikria says.

So for now, Dr. Zikria says this study doesn’t make him want to change his recommendations to patients who’ve had total knee replacements.

“If they tell me at 15 years there’s no difference in the two groups of people then maybe I would change my opinion. But at seven-and-a-half years, it wouldn’t change the way I practice,” Dr. Zikria says.  “Just because something is good in the short-term doesn’t mean it will be good in the long-term.”

Dr. Parratte understands that it is too early to expect doctors to change their recommendations for knee replacement patients when it comes to what sports they should and should not take part in. But he says if further studies back up these results, it could happen someday.

“It’s good news for the patient, good news for the surgeon; and we have to keep on working on this for the future,” Dr. Parratte says.