How to Know When It’s Safe to Run Through Knee Pain and When You Need to Stop

Of all the aches and pains that can plague runners, knee pain is one of the most common. As a doctor of physical therapy, patients often ask me when it’s OK to run with knee pain and when running through it could lead to a worse injury. As a runner myself, I’m guilty of running with knee pain when I should probably be taking a break. If you’re anything like me, it takes a significant amount of pain to actually get you to stop running, but the truth is, that’s not always the best approach.

Knee pain comes in many forms. It can be sharp, dull, achy, zinging, shocking, or creaky.

Physical therapists do our best to quantify pain, with numerical scales and questionnaires about how much pain affects function, such as the popular 0-10 pain scale. But ultimately, pain can be very subjective. For some people, a light ache can cause them to yelp when they bend their knee. Others (like many of my patients training to run a marathon) will grin and bear it, running through any amount of knee pain as long as they think they aren’t permanently damaging their bodies. While the techniques and scales we have for measuring pain are very helpful in quantifying and categorizing pain, they don’t necessarily tell us when any given person should stop running or keep going, because pain is so individualized.

That said, there are some general guidelines to follow if you’re trying to decipher between an annoying ache and a real injury.

Knee pain can be caused by a handful of different conditions.

Common conditions include runner’s knee (or patellofemoral pain syndrome), IT (iliotibial) band syndrome, ligament tears (ACL and MCL tears being the most common), and meniscus tears (a tear of the cartilage in the knee joint). Some of the aches and pains associated with these conditions might go away with the right glutes-, quad-, or hip-strengthening regimen, serious foam rolling, footwear changes, and certain stretches. But some require more attention, including rest and/or physical therapy.

Runner’s knee is the most common culprit of running-related knee pain, though there are a few similar, not-too-serious conditions that runners may experience.

According to research, approximately 25 percent of running-related injuries are attributed to patellofemoral pain syndrome (PFPS), or “runner’s knee.” In my experience, the number of women affected by this condition is significantly higher than the number of men due in part to the angle that women’s wider hips create at the knee joint. Runner’s knee can feel like a dull, diffuse ache in and around the kneecap. It is caused by muscle imbalances (like weak hips or an asymmetry in quad strength) that cause the knee cap to shift out of place as you bend and straighten your leg, ultimately leading to irritation in and around the joint.

Runner’s knee can often lead to chondromalacia, a condition that develops when the cartilage under the kneecap becomes rough with repeated wear and tear. This “roughening” causes increased friction below the joint’s surface, leading to irritation, inflammation, and pain.

IT band syndrome (ITBS) is also an overuse injury. The IT band is a band of fascia (connective tissue) that extends from the hip to just below the knee. It acts as a stabilizer during running, and overuse or a quick increase in training volume (as well as biomechanical factors like hip weakness) can cause it to become irritated.

Symptoms of PFPS, chondromalacia, and ITBS usually intensify with single-leg plyometric exercising such as running. But despite being uncomfortable, it is usually OK to run with these symptoms, as long as you are simultaneously addressing the cause of your pain. Depending on the cause of your pain, this can include the various treatments mentioned above: working on strengthening your hips and quads, stretching your lower body, and using myofascial release techniques such as foam rolling on the tight spots. (Of course, if your doctor says otherwise for your specific case, always listen to them.)

If knee pain is more sharp, frequent, or intense, or if it leads to a feeling of instability, “catching” (like you can’t fully bend or straighten your knee), or buckling, it may be a more urgent issue.

Structural problems such as ligament or meniscus tears are usually another story. These injuries, by definition, suggest damage to one of the stabilizing structures in the knee joint. Symptoms of instability, swelling, limited range of motion, and higher levels of pain are more common with these injuries and are all signs that you should have your knee examined by a professional before returning to running.

If you can rate your pain under a 4 out of 10 (with 10 being the worst pain of your life), running on it might be OK.

That said, any small amount of pain is a signal to your body that there is likely a vulnerability, like a weakness elsewhere contributing to poor body mechanics. Weakness and tightness, thankfully, can be addressed with the right strengthening and stretching routine. If you don’t address your symptoms, though, a relatively small pain from something like runner’s knee can lead to a more problematic, acute injury like a ligament tear. So, if you decide to run through the pain of something relatively minor like runner’s knee, make sure you’re also addressing the cause of the problem.

And if your knee pain ever intensifies to the point where it’s difficult to perform daily activities, like walking or going up and down stairs, then (as a general rule) running on it is not a good idea. Running forces you to load each leg one at a time with your full body weight, plus the force of gravity. Anything you feel while walking will be exaggerated and intensified with running, making your knee, along with the rest of your body, more vulnerable to injury.

Still not sure if you need to stop running? My advice is to see a physical therapist before the pain gets worse.

A physical therapist can analyze your movement, look at your gait and the mechanics of your whole body, and identify what may be the true source of the problem. Why did one knee get injured and not the other? Maybe it's because of chronic weakness in that one hip. Maybe that ankle sprain 10 years ago made you favor one side. Simply getting a diagnosis from an M.D. is a start, but it takes really analyzing your movement to understand why your pain is there and how to get rid of it.

Knee pain may come and go, but if it doesn't disappear completely after a few weeks (even if it’s mild) or is bad enough that it is making you stop doing something you love (like running!), then it’s time to get it checked out if you haven’t already. Schedule a visit with a physical therapist or an M.D. who can properly assess what’s going on. Thankfully, most running-related knee injuries are from overuse and not traumatic accidents, which means there are ways to intervene.

For many runners, knee pain is just part of the sport they love. I, too, have worked through my own running-related knee injuries. I wore an immobilizing knee brace for months while living in a fifth-floor walk-up—I know the struggle. But pain is a really important signal that something is going on in your body, and it’s up to you to listen to and translate the message. Ultimately, knowing how your body usually feels and listening to those pain signals is the best way to avoid bigger injuries and maximize the time you get to spend out there blissfully logging miles.