What gives? Well, it might be a little condition known as runner's knee.

What is runners knee?

Runner's knee is an umbrella term used to describe a misalignment in the knee caused by a strain or a natural misalignment of a joint (a.k.a. if you have knock knees) or wide-set hips, says Cardelia Carter, M.D., an orthopedic surgeon and the director of the Womens Sports Medicine Center at NYU Langone Health.

This Is Why You Get Knee Pain While Running
This Is Why You Get Knee Pain While Running

Generally, you'll feel this pain at the side of the knee, or behind the knee cap as you bend and straighten. Carter says itll feel very different from the knee pain you might deal with after bumping into something, for example. Instead, "runners knee pain appears gradually and seems to be worse with physical activities."

Since the condition is exacerbated by repetitive impact activities, runner's knee is a super common overuse injury for those who like to pound the pavement. But you dont actually need to be a runner to feel it, she says. People might feel runners knee pain while squatting or lunging too deeply, from taking the stairs, or from sitting for extended periods of time.

What causes knee pain while running?

To maintain pain-free knees, the muscles from your core down to your ankles need to work in sync to support your joints. But if these muscles are too weak to keep your hips and ankles in their proper place, the pain will centralize at your knees. So, unfortunately, whether or not youre hit with runners knee is pretty much out of your hands, since it depends on how youre built.

Naturally weak or under-active hips, for example, will cause your knees to collapse toward each other during any activity where weight is carried through the leg. (Think: jumping or climbing stairs or running on concrete.) And if your core isnt strong enough to keep your hips steady, your knees will be forced to do the hard work of stabilizing your body. Cue pain.

And the sour cherry on top, says Carter, is that the lower limb misalignments that cause runners knee pain-wide-set pelvises, out-turned thighs-are more common in female bodies.

Now, before you go cursing your knees (that, may I remind you, have been working hard to carry you all your life), you should note runners knee is common and treatable.

So how do I make knee pain go away?

Get VERY friendly with stretching and strengthening because theyre both going to become big parts of your life if you want to cut runners knee off at thewell, knees.

Recovering from runners knee is about "retraining the way that you move" and coming up with modifications that will allow you to go easy on your knees, says Meghan Cass, a D.P.T., a physical therapist. And the best way to do that is with physical therapy.

Once a therapist has pinpointed the aggravating factor-like stiff ankles or the intensity of your exercise regimen-she can create a rehabilitative routine, says Cass. This might include modifying where you run (grass vs. road) or how deeply you lunge and squat.

You'll also do moves that will strengthen your core and your inner thighs, or stretch your calves, in an effort to better position your knee for physical activity. A PT might also encourage you to mix different types of workouts into your regular routine, says Carter, such as yoga or swimming to replace a running or squatting session.

These methods wont act like vaccines though, Carter warns. Youll need continuous doses of knee-strengthening exercises to keep the pain from coming back.

And extra TLC, like icing the knee for 20 minutes, might also help, says Cass.

One important thing to note: If you experience knee pain while you sleep, or you notice swelling around your knee cap, you might be dealing with something more serious than runners knee. In this case, Cass suggests making an appointment with your doctor.

What can I do to prevent it?

In order to keep the pain from coming back, Cass says to stick to the strengthening exercises, stretches, and modifications that helped you get rid of it in the first place. Once your knee pain starts diminishing, you can take what youve learned home with you and reduce your visits to the PT. Her go-to, at-home moves are:

1. Foam rolling

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Cass is a fan of rolling your calves or thighs over a foam roller to release tightness and tension in the muscles.

2. Calf stretch

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How to: Place the ball of your right foot into the loop of a strap. Raise leg so its almost perpendicular to the surface youre on. Flex the foot by pointing toes toward your chest. After a a few seconds, relax by pointing toes toward the ceiling before repeating the movement. Repeat on opposite side.

Or, try facing a wall, place one foot about two feet back, keeping that heel on the ground. Then, lean forward into your other foot with your hands straight out in front of you and against the wall.

3. Kneeling hip flexor stretch

Cass says this is great for addressing hip tightness and knee tightness. Get down on one knee and lean forward pushing your hips toward the ground, hold for 30 seconds, then switch .

4. Plank

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How to: Start on the floor on your hands and knees. Lower your forearms to the floor with elbows positioned under your shoulders and your hands shoulder-width apart. Your arms should form a 90-degree angle. Maintain a straight line from heels through the top of your head, looking down at the floor, with gaze slightly in front of your face. Tighten your abs and hold.

"Planks can be varied in so many different ways," says Cass. She likes to build on difficulty as her clients get stronger. When they start out, though, she has them get down onto their forearms and toes , and hold.

5. Clam shell

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How to: Lie on your left side and place your left forearm on the floor. Bend your knees and stack your right leg on top of your left leg, with your left hip resting on the ground. Rotate your right knee toward the ceiling, keeping your feet together. Lower your leg, keeping your hips raised throughout. That's one rep.

These are great for the hips, says Cass. For an extra challenge, Cass suggests trying this move with a resistance band around your knees.

6. Banded exercises

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How to: Stand with feet hip-width apart, knees slightly bent, with a resistance band around your ankles. Maintaining a tight core, step your left foot out to the side, followed by your right. Then step back to the left. Thats one rep.

Cass is all about adding a resistance band around your ankles during this side-step move, along with a resistance band around your thighs while squatting .

7. Single-leg activities

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How to: Stand on your left leg with your right palm facing towards your thighs. Extend your left arm to the side for balance. Keep your left leg slightly bent. Lean forward, extending right leg straight behind you, until your torso is parallel to the floor, and your hand is almost touching the floor. Drive into your left heel to return to the standing position. Thats one rep.

Single-leg moves are great for making sure runners "are very strong and have good balance when theyre standing on just one leg." Cass usually has clients do single-leg deadlifts (pictured above) and single-leg hops. She also has clients try single leg sit-to-stands where you slowly lower yourself to a chair while balancing on one leg, "focusing on sitting back into the chair and not letting your knee fall in toward the other leg," she says.

Incorporating a mix of these exercises into your daily routine is a good move toward improving and preventing runner's knee. "Variety is the best way to avoid injury," says Carter.