Cycling is easy on the knees...if your bike fits you.

RODALE NEWS, EMMAUS PA—Osteoarthritis is sometimes called “wear-and-tear arthritis,” because it’s what happens when the cartilage that protects your bones wears away after heavy, repeated use. To protect knees that may be prone to osteoarthritis (because, say, you’re older or overweight) from excessive wear and tear, the American Academy of Orthopaedic Surgeons actually suggests, among many things, switching from running or jumping exercises to non-weight-bearing activities like cycling to minimize stress on the knees. Which is why the results of a new study that found daily bicycling to be a risk factor for knee osteoarthritis were so surprising.

THE DETAILS: Researchers at the Tehran University of Medical Sciences in Iran set out to measure daily activities that might be related to the development of knee osteoarthritis, a degenerative condition that most often affects middle-aged and older people in which cartilage in the knee joint gradually wears away, causing pain and stiffness in the knee. Activities they studied included kneeling and squatting, climbing stairs, and lifting and carrying heavy loads. The scientists recruited 480 people (average age 57) with knee osteoarthritis—Plus, they recruited 490 controls, or people without knee osteoarthritis.

All study participants received questionnaires in which they recorded their occupations, and the time per day they spent on sports and 10 daily activities identified by the researchers. The activities included standing, walking, sitting, squatting, knee-bending, cycling, lifting, and climbing. After adjusting for age (the older you are, the more wear and tear your knees have experienced, and the more likely you are to develop osteoarthritis), sex, and body-mass index (the heavier you are, the more wear and tear your knees experience, and the more likely you are to develop osteoarthritis), the two activities they found to be risk factors for knee osteoarthritis were squatting more than 30 minutes per day and cycling, also more than 30 minutes per day, particularly in men.

WHAT IT MEANS: Irrespective of age, and weight, repetitive movements in some daily activities increase the risk of knee osteoarthritis. Squatting, say the study authors, was no surprise, having been proven in prior studies to be a risk factor for knee osteoarthritis. In fact, they cite another study, whose authors think that repeated squatting has “significant implications for the long-term mechanical function and structural integrity of the joint cartilage.” Cycling, however, is a different story.

“Cycling is considered to be low-impact on the knees,” says Mike Cushionbury, an editor at Bicycling magazine. “But there are a few bike fit mistakes that can void that." The most common, he says, is keeping the saddle too low. When that happens, your really only using your thighs to pedal, instead of the entire leg. That creates extra pressure on the knee joint, which can cause damage to your knees.