When your knees hurt climbing the stairs, you don’t exactly feel like jumping for joy. But that may be exactly what you need to do to strengthen the cartilage in your knees and slow the progression of osteoarthritis. While you shouldn’t run outside and starting playing hopscotch right away, a carefully structured jumping program may benefit your knees without hurting them.


Until now, high-impact exercise has been thought to be harmful to people with knee arthritis. The surprising finding that it may not only be safe but actually beneficial comes from a new Finnish study. It helps build knee cartilage, which no- or low-impact aerobic exercise has not been shown to do.

The researchers looked at the effect of a high-impact exercise program on knee cartilage, osteoarthritis symptoms and physical function in 76 women, ages 50 to 65, who had knee pain on most days. The women had patellofemoral joint osteoarthritis, a common form of the disease that causes pain under the kneecap (aka the patella) and often makes climbing stairs painful. Sound familiar? Men often get this kind of knee arthritis, too, so let’s all pay attention.

The women were randomly assigned to either an exercise group or a control group. The control group went about their normal daily routines. The exercise group went to supervised classes of about an hour three times a week.

Their jumping exercises started out very gentle and gradually increased in intensity. The women did aerobics while jumping over foam blocks that were two inches from the ground and jumped up and down steps that were four inches high. Every three months, the heights were raised until eventually they were about eight inches for both the aerobics and the steps. There were no deep squats. (Squats can be very tough on knees.) On average, each exerciser did 44 high-impact jumps per exercise session, which is less pounding than you’d get from, say, running for the same amount of time. A few women (six, to be exact) had some joint problems at one time or another, but they just took a week or more off and then returned to the classes.

The results were modest but significant. At the end of the 12-month period, the investigators found that when measured via magnetic resonance imaging (MRI), the thickness of the kneecap cartilage among women assigned to the jumping group had a 7% increase. For the control-group there was no improvement. They also found the knee extension force of those in the jumping group increased by 11% compared with controls. Self-reported pain was about the same in the jumping and the control group. The women got a little fitter, too. Added bonus: Although this study did not look at bone strength, high-impact exercise is exactly what’s been shown to help strengthen bones against osteoporosis.


The current study suggests that adding a little jumping—carefully—to your routine might be reasonable. But don’t neglect low-impact exercises such as cycling or aquatic classes either. In the end, any exercise that doesn’t hurt you is good for your knees. You might call it the arthritis paradox—it may hurt to be active, but being active reduces the hurt. When it comes to the knees in particular, there is growing evidence that exercise reduces pain and improves function.

Being more active may also help you lose weight and, according to Derek H. Ochiai, a sports medicine specialist at Nirschl Orthopedic Center in Arlington, Virginia, it’s amazing how little weight loss it takes to reduce the pressure on your knees. Dr. Ochiai often asks his patients: “If you put a five-pound backpack on your back and walked around and went through your daily routine for a day, and then the next day you took off the backpack, would your knees have felt better with the backpack on or off?”

For gym rats, Dr. Ochiai recommends the elliptical machine, the recumbent bike and, of course, swimming. “That is a great aerobic exercise and it puts very little pressure on your knees,” he explained. The stair climber is a little too much stress on the knees, though.Whatever you do, start off slowly and build up intensity gradually, just as the women in this study did. Yes, your doctor can give you a brace—or injections. But only you can take control through exercise. Says Dr. Ochiai, “You can start to improve your situation by stuff you can do yourself.”