Biking, Walking Best for New Knees

By Kathleen Doheny
HealthDay Reporter
Thursday, March 6, 2008; 1:00 PM

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THURSDAY, March 6 (HealthDay News) -- The thousands of Americans who undergo knee replacement surgeries each year may want to put away their tennis rackets and get back on their bikes, a new study shows.

Biking and treadmill walking appear to be two of the gentlest exercises for those who have had a knee replaced with an artificial joint, researchers found, while higher impact sports such as jogging and tennis generated higher forces on new knees, according to study author Dr. Darryl D'Lima, director of the Orthopaedic Research Laboratory at Scripps Clinic, in La Jolla, Calif.

More surprisingly, golf swings were also tough on the knees, although D'Lima was quick to point out the swings make up just part of the exercise in a round of golf.

He is scheduled to present his research Thursday at the American Academy of Orthopaedic Surgeon's annual meeting in San Francisco. The study was initiated by Dr. Clifford W. Colwell, director of the Shiley Center for Orthopaedic Research & Education at Scripps.

An estimated 478,000 total knee replacement surgeries, called total knee arthoplasties (TKAs), are done in the United States each year, according to the researchers. In the surgery, the original joint is replaced by one made of various materials, such as plastic and metal.

Surgeons typically advise patients to resume physical activity when they are able. But advice about which activity is best has been subjective, D'Lima said. So, his team decided to measure forces on the knee while patients took part in a variety of exercises.

In the study, D'Lima's team measured forces on the tibia, or shinbone, in four patients who had undergone TKA. These four patients had a specially designed joint that allowed forces to be measured from inside the implant.

A year after their surgery, each of the four patients jogged, played tennis, did golf swings, walked (on a treadmill and on level ground) and biked while the forces to their knee area were measured.

Golf swings produced forces of 4.5 times body weight on the forward knee and 3.2 times body weight in the opposite knee, the researchers found.