Is running actually bad for your knees?

The most common running injuries hit the knees. But running isn't to blame.

"Running gets a bad rap, but running can strengthen the knee, and those who run throughout their lives have stronger knees than those who don't," according to physical therapist Michael Silverman, P.T., M.S.P.T., coordinator of the Tisch Performance Center at the Hospital for Special Surgery.

In fact, the largest study of runners ever completed, which was recently published in Medicine & Science in Sports & Exercise, concluded that running does not increase the risk of osteoarthritis (cartilage breakdown), even in marathoners. And, get this: Runners had half the incidence of knee osteoarthritis compared to walkers.

The reason: "Running has been shown to thicken the cartilage in your knee," says Jason Fitzgerald, a USA Track & Field-certified coach and the founder of Strength Running. "The body adapts to running and gets stronger, after all. And since running doesn't involve excessive bending of the knee nor much twisting or turning, it's a very safe form of exercise for knees." Plus, high-impact exercises like running spur bone growth and strengthen the muscles around the knee, thereby taking pressure off the joint, Silverman says.

Still, if you do have runner's knee, that's of little help. So what should you do if you can't take a step without a knee brace? Strengthen your weak spots. Virtually all running injuries to the knee are caused by muscular imbalances, Silverman says.

"With common faculty biomechanics, you can end up overloading the inside of the knee, making you more prone to meniscus tears," Silverman says. "Or if you are weak in the hips, your muscle imbalance forces the leg to pull in during mid-stance. Your IT band has to work more then to try to pull the knee back to where it should be, and it gets tight."

The best way to reduce your risk of knee injuries while running is to strength train—particularly the glutes and hips, where underlying weaknesses often lie. Exercises such as the straight-leg raise, clamshell, bridge, and squats can help.

Also, until you fix any imbalances, you may need to back off from running for a bit. "Running can exacerbate existing knee injuries, so if you're currently dealing with a knee problem, it's best to get healthy first before you start running," Fitzgerald says. (If you have a have "moderate" or "severe" case of osteoarthritis—which can be caused by a hereditary disorder or being overweight, for instance—running can be painful and should be avoided, according to Silverman. If it's mild, then it's usually okay to run.)

Fitzgerald also advises against increasing your mileage too quickly. Once you've reached a good "baseline mileage," what you're comfortable running each week, any increases should be pretty small, between 5 and 10 percent, every other week. Remember that when it comes to becoming a better runner, consistency is more important than huge jumps in mileage.

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