Everything You Need to Know About Runner's Knee—Even If You're Not a Runner

Unlike many other bones, your kneecap floats freely, moving back and forth as you bend your leg. In a perfect world, it would travel in a straight line along the groove at the end of your thighbone, or femur.

But several factors—including muscle weakness, tightness, and imbalances—can throw off your alignment, driving the kneecap off track, says Kevin Vincent, MD, PhD, medical director of the University of Florida Sports Performance Center. The kneecap then rubs against the thighbone, causing knee pain and swelling that often worsens with activity.

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Though you'll feel the ache in your knee, the true source of the discomfort from patellofemoral pain syndrome usually lies above or below the knee joint. Weak muscles in your hips and core most often take the blame, Holland says. They're designed to hold your pelvis and thighs in the proper position as you move—when they aren't up to the task, your knees drift inward, driving your kneecap out of alignment.

In other cases, the issue starts from the ground up. The way your foot strikes the ground with each step can also throw your knee off track, Holland says. Weaknesses in muscles that stabilize your lower leg and flex your toes can also contribute to knee pain, she says.

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Unlike a sudden, traumatic knee injury—such as banging your knee on a table or tearing a ligament—runner's knee develops slowly. Often, you'll first feel discomfort or notice swelling during or immediately after running or other activities. You might also notice pain going up and down stairs, when you stand up or sit down, or any other time you're transitioning between positions.

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Another giveaway that you might have runner's knee: You can't sit through a movie or long flight without pain that causes you to straighten your leg, says orthopedic surgeon Christopher Ka​eding, MD, of the Ohio State University Wexner Medical Center. In a bent position with your quad muscles at rest, your kneecap is forced back against the thighbone, triggering knee pain and irritation.

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Runners have a high rate of patellofemoral pain syndrome, in part because the motion of running involves bending the knee so many times. Essentially, running is a series of around 1,700 one-legged squats per mile, Dr. Vincent says. If you're out of alignment, that's a lot of bone-on-bone contact.

People who play sports that involve running and jumping, such as soccer and basketball, also face a high risk of runner's knee. And certain exercises at the gym, such as deep squats, may contribute to this type of knee pain as well, says Kevin Plancher, MD, a sports medicine specialist in New York.

Women appear more likely to develop runner's knee than men. The reason could relate to the shape of the pelvis and the angle at which the quad muscle and knee align in women, but experts aren't entirely sure, Dr. Kaeding says.

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For mild cases of knee pain and swelling, you can try self-care and home treatment. Ice, anti-inflammatory medications like ibuprofen or naproxen, and cutting back on activities that cause knee pain can help. Some people use tape or knee braces, but studies suggest these work best when you combine them with exercise programs.

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If you have knee pain that lingers for three weeks or longer, worsens during or after exercise, or interferes with the way you walk or run, it's time to visit a doctor or physical therapist. "The faster you get treated, the faster you'll recover" from runner's knee, Holland says. Though it's rare, untreated cases of runner's knee can result in permanent damage to knee cartilage.

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Many other conditions can cause knee pain—and some feel similar to runner's knee. This includes small cracks in the kneecap called stress fractures, tendonitis, torn ligaments, cysts, and arthritis. Some people—especially older folks—can have arthritis and runner's knee at the same time.

There's no single test that pinpoints patellofemoral pain syndrome. Sometimes, your doctor can diagnose it by asking you about your symptoms, examining you, and watching your knees as you perform movements like one-legged squats. In other cases, he or she may order X-rays, an MRI, or other imaging tests to rule out other knee injuries or conditions, Dr. Kaeding says.

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Physical therapy is usually the first line of treatment for runner's knee when home care isn't enough, Dr. Kaeding says. You'll undergo assessments of your strength and alignment and receive a tailored program of exercises to build muscle, especially in your core and hips. Stretching the muscles in your glutes, thighs, and calves may also improve alignment and decrease knee pain.

Holland has seen dedicated patients with mild runner's knee improve in as little as two weeks, she says, but that's not typical. Often, relief takes six weeks or longer. In rare cases, physical therapy isn't effective. In these instances, surgery can often realign the kneecap or remove damaged tissue to reduce knee pain.

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About a quarter of people diagnosed with runner's knee will give up their recreational sports, but most people—even runners—with patellofemoral pain syndrome can safely keep moving, Dr. Vincent says. You just might have to cut back a little until your strength and alignment improve. For example, you might be able to run three miles without pain but not four. Orthotics for your shoes may also temporarily make you feel better.

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Gait retraining—where a physical therapist recommends specific ways to change the way you walk or run—also appears to help ease runner's knee pain, especially in combination with a strengthening program.

In general, taking shorter, faster steps takes pressure off your knees, Dr. Vincent says. If you run, he recommends counting the number of steps you take per minute. Get a number below 160? Speeding it up by 5 to 10% can reduce the load on your joints and alleviate knee pain.

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The same types of hip- and core-strengthening exercises that treat runner's knee can also prevent it from occurring in the first place. Consider working some into your routine, especially if you're a runner or play a sport like basketball or soccer. Cross-training—doing activities other than running, like biking or swimming—may also help, Dr. Plancher says.

If you're starting a new exercise program or ramping up an existing one, doing so slowly can also protect your knee health. A good rule of thumb is to increase your mileage or the amount of time you spend doing any single activity by no more than 10% total per week. And pick up a good pair of shoes specifically designed for the sport you regularly participate in—this can provide the support you need to stay pain-free, Dr. Kaeding says.

This post was originally published on August 14, 2017 and updated for accuracy.