Biking, Walking Best for New Knees

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D'Lima noted that the forces produced by the golf swing, however, occur in an instant, while the forces produced by jogging are constant. "I think golf should be OK," he said. "It's more of scientific interest."

There were some other surprises, D'Lima said. "We expected that walking on a treadmill, which is more controlled, would be better than biking [in terms of low impact to the knee]," the researcher noted. But biking actually won out, he said.

Other details on the results:

• Biking generated the least force, producing impact of about 1.3 times the person's body weight.
• Treadmill walking was next best, producing forces of 2.05 the body weight.
• Walking on level ground generated forces of 2.6 times the body weight.
• Tennis produced forces of 3.1 to 3.8 times the body weight, with serving producing the highest impact.
• Jogging produced forces of 4.3 times body weight.

Modification of certain high-impact exercises could help, he said. For avid golfers, "it's possible you could modify your swing," D'Lima says. Golfers could get a high-tech evaluation of their swings, offered by many golf club makers, or ask their pro about modifying the swing to exert less force on their knee, D'Lima suggested.

However, for more strenuous high-impact pursuits such as jogging, people who've undergone knee replacement should make a permanent switch to another form of exercise, the expert said.

Dr. Daniel Oakes, a staff orthopedic surgeon at Santa Monica-UCLA & Orthopaedic Hospital in Santa Monica, Calif., said the study confirms advice he generally gives to his knee-replacement patients.

"We strongly dissuade [them from] jogging," he said. "I tell them activities that are OK are walking, biking, hiking, riding an exercise bike, riding an elliptical trainer and walking on the treadmill."

He suggests doubles tennis, not singles, since it is not as aggressive. He generally allows downhill or cross-country skiers to resume that sport when they are healed. And he thinks golf is fine.

While the study confirms the experts' suspicions about which activities are more stressful on the new knee, it can't be determined from the study if the increased forces will lead to a higher failure rate in the joint, said Oakes, who is also an assistant professor of orthopedic surgery and chief of the joint replacement service at the University of California Los Angeles' David Geffen School of Medicine.

More information

To learn more about knee replacement, visit the American Academy of Orthopaedic Surgeon.