Why Your Knee Hurts When You Run (And Why Rest Alone Won't Fix It)
Written by Dr. Emilly Hill, PT, DPT, Running Specialist
If you have been running in Boulder long enough, you have probably either had knee pain or have a running buddy who has. Runner's knee is the most common injury we see at Atomic Physical Therapy, and it is also the most misunderstood. Most runners try to wait it out, ice it, take a few days off, and then go right back to running the same way they were before. Then it comes back. Sound familiar?
Here is what is actually going on, and what to do about it.
What runner's knee actually is
Runner's knee is a catch-all term. The medical version is patellofemoral pain syndrome, or PFPS. It usually shows up as a dull ache around the front of the kneecap, sometimes underneath it. It tends to get worse on downhills, going down stairs, or after sitting for a while with your knees bent.
The pain itself is real, but it is almost never the actual problem. The knee is usually the messenger. The cause is somewhere else.
Why it happens
The knee is a hinge. It mostly just bends and straightens. What controls how well it does that is everything above and below it. So when something at the hip is not pulling its weight, or something at the foot and ankle is not absorbing force properly, the knee ends up taking the load it was not designed to take.
The most common drivers we see in runners:
Weak or undertrained hips, especially the glute med
Quad dominance with limited glute engagement
Poor cadence (overstriding puts huge load on the front of the knee)
A sudden bump in mileage or hill work
Worn out shoes
Tight calves and limited ankle mobility
Notice none of that is actually about the knee. That is the point.
Knee pain that won't go away? Emily Hill is our RunDNA-certified running PT and works with Boulder runners every week to figure out exactly what's driving knee pain and build a plan to get them back out there. Book a free discovery visit with Emily
Why rest alone does not fix it
This is the part that surprises people. Resting takes the symptoms away. It does not fix the cause. So you rest for two weeks, you start running again, and the same load goes back through the same poorly supported knee. Within a few weeks you are right back where you started. We see this loop constantly
Rest is part of the recovery, but it is not the whole plan. You also need to figure out why the knee got loaded that way in the first place and address that.
What actually works
Three things, roughly in order:
Identify the source. A real running assessment looks at your hips, your gait, your cadence, your shoe wear, and how you are actually loading the knee when you run. At Atomic PT we use Boulder’s only 3D gait analysis system that gives us hard data on what your body is doing, not just what we can see by eye.
Strengthen what is weak. Almost every runner's knee case I see has a hip strength piece to it. Single leg work, glute med specifically, posterior chain. This is non-negotiable.
Adjust the running itself. Sometimes the fix is as simple as a small cadence change or shortening your stride. Sometimes it is dialing back mileage temporarily while you build the strength to handle it. Most of the time it is a combination.
What is not a long-term fix: just stretching the IT band, foam rolling forever, knee sleeves, or running through it.
When to come in
If you are dealing with knee pain that has lasted more than two weeks, or pain that keeps coming back any time you ramp mileage, that is your signal. The longer you wait, the more your body compensates around it, and the longer the fix takes.
We see a lot of runners in Boulder who waited too long because the pain was "just annoying" until it suddenly was not. Catching it early is the difference between a few weeks of targeted work and months of frustration.
Ready to actually fix it? Emily Hill works with Boulder and Broomfield runners at all three Atomic PT locations and uses RunDNA 3D gait analysis to find what is really driving your knee pain. Book a free discovery visit with Emily
