Doctors have long recommended that knee replacement patients avoid sports like football, soccer, aerobics, jogging, baseball and basketball because it was thought that high-impact activities might contribute to the early failure of artificial joints, leading to the need for a second surgery. 

But a study suggests that those long-held assumptions could be wrong.

The study compared two groups of people with knee implants  – those who ignored advice to take it easy on their new joints (called the sport group) and model patients who followed doctors' orders to avoid high-impact activities (the control group). 

Researchers found that after more than seven years there were no significant differences in wear or mechanical failure between the two groups.

The research was presented at the 2010 annual meeting of the American Academy of Orthopaedic Surgeons in New Orleans, La.

“We were a little bit surprised because we were not thinking that there would be absolutely no difference,” says lead author Sebastian Parratte, MD, PhD, an orthopaedic surgeon from the Mayo Clinic in Rochester, Minn., and the Aix-Marseille University, Center for Arthritis Surgery, Hospital Sainte-Marguerite in Marseille, France.

“Before, everybody was thinking if you go running or something like that it will kill the prosthetic and don’t do that. It’s forbidden,” Dr. Parratte says

Perhaps even more surprising is that researchers found that those who took part in the non-recommended sports actually showed higher knee and function scores than the control group.

The control group had a higher rate of loosening, wear, fracture and overall mechanical implant failure than the sport group at 11 percent compared to 8.5 percent in the sport group.

Adjusting for a variety of lifestyle factors, doctors say the sport group had a 10 percent increased risk of mechanical failure, but they don’t consider that to be statistically significant.

“The big news is that everybody before was thinking that doing high-activity sports would be terrible for the prosthetic of the patient and what we discovered was it was not terrible and indeed the patients that did high-level activity sports were doing better than others,” Dr. Parratte says.