Runner's Knee Hidden Cause: Lower Back Dysfunction
By Grant Frost · Physiotherapist • Last clinically reviewed: 15 June 2026

June 15, 2026

Key insights: 60-second read

Runner's knee is often caused by lower back dysfunction, not the knee itself - hidden stiffness and restriction at the base of the rib cage and top of the lower back changes how you load your knee over time.
Running exposes hidden dysfunction - it doesn't cause it - running is normal and healthy. It simply reveals the underlying mechanical issues you have taken into the activity.
Two simple exercises can provide immediate relief - lower back mobility work (foam roller or lacrosse ball) and the couch stretch for tight quads.
Test-retest proves the connection - test your knee pain (squats, stairs, running), perform the exercises, then re-test. If your symptoms change, you have identified the source.
Your sitting posture may be the root cause - the way you sit at a desk, on the couch, or in the car may be the hidden reason your knee hurts when you run.

If you have been struggling with runner's knee, patellar tendinitis, or patellar tendinopathy (pain just underneath your kneecap at the tendon that anchors to the top of your shin bone), you have probably been told to rest, ice, stretch your quad, and maybe stop running.

While rest may calm things down temporarily, the pain often returns as soon as you start running again. Why? Because you've likely treated the symptom, not the potential cause.

In my 20 years as a physiotherapist, I have found that the hidden cause of runner's knee is often lower back dysfunction - specifically at the base of your rib cage and the top of your lower back. Hidden restrictions, stiffness, and tightness in this area change the way you load your knee over time.

This video and article will show you two simple exercises to test this connection and potentially provide immediate relief.

"Running can be the thing that exposes it and irritates it, not because it is bad for you. In fact, it is the opposite. It is fantastic for you. But the repetition and the time frames associated with running can be really good at exposing hidden underlying dysfunction you have taken into running."

On this page

The hidden cause: lower back dysfunction Test-retest: where are you starting? Exercise 1: Lower back mobility (foam roller or lacrosse ball) Exercise 2: The couch stretch for quad tightness The sitting connection: why your posture matters From my clinical experience Frequently asked questions

The hidden cause: lower back dysfunction

When we talk about runner's knee or patellar tendinopathy, the pain is very real and very specific - just underneath the kneecap. But if we only look at the knee, we miss the bigger picture.

In my clinical experience, the hidden cause of this condition is lower back dysfunction at the base of the rib cage and the top of the lower back. Hidden restrictions, stiffness, and tightness in this area change the way you load your knee over time.

This does not mean you have a bulging disc or a serious back problem. It simply means that certain segments of your spine may have become stiff, tight, and overloaded - often without you even realising it. And this dysfunction travels down the kinetic chain, affecting how your knee is loaded when you run.

The missing perspective

"The biggest missed perspective here is that the hidden cause of runner's knee is actually lower back dysfunction - not at the base of your spine, but at the base of your rib cage and the top of your lower back."

Test-retest: where are you starting?

Before you do any exercises, you need to establish a baseline. This is the test-retest principle, and it is the only way to know whether this approach is relevant for you.

Test your knee pain: Do something that you know alerts you to your patellar tendinopathy. This could be:

Deep squats
Going for a jog or run
Walking up and down stairs
A brisk walk

Take note of how your knee feels - how sore it is, how easy the movement was, where exactly you feel it. This is your baseline.

After you complete the exercises below, you will perform the exact same movement again to see if anything has changed.

"We always want to do something first that lets you know how your knee pain feels in the moment. Get a sense of how it feels, how sore it is, how easy it was to do, because we are going to come back to this immediately after each exercise."

Exercise 1: Lower back mobility (foam roller or lacrosse ball)

What you need: A foam roller, lacrosse ball, tennis ball, or even a rolled-up towel.

Where to focus: The base of your rib cage and the top of your lower back (thoracolumbar junction). This is the area where hidden restrictions often hide.

Step-by-step:

Place the foam roller or ball at the base of your rib cage, roughly in the middle of your back.
Gently recline back onto it. You can do this with your hips on the ground (gentler) or by bridging up with your head and shoulders on the ground and dropping your hips down (more pressure).
Roll slightly to one side and note how it feels. Then roll to the other side.
One side will likely feel more restricted - thicker, tighter, more dense, less able to sink in compared to the other side.
Important: Regardless of which knee hurts, the spinal dysfunction may be on either side. Do not assume it is the same side as your painful knee. Test both sides and focus on the side that feels most restricted.
Once you have found a restricted spot, stay there for 30-60 seconds. Take deep, slow breaths to help your nervous system relax and allow the tissue to release.
Systematically move the roller or ball up and down, hunting for other areas that feel stiff and restricted.

Re-test immediately: Stand up, walk around, and repeat the same movement you tested at the beginning (squats, stairs, running). Has your knee pain changed? If it has, you have just proven that your lower back is connected to your knee pain.

Which side to work on?

"If you have left-sided jumper's knee and you roll slightly to the right side of your spine and it feels the most restricted, this is where you need to be. This is where the mechanical handbrake may be that is pulling a bunch of slack out of your left-hand side."

Exercise 2: The couch stretch for quad tightness

When the lower back is dysfunctional, the quadriceps muscles at the front of your thigh often become tight as a compensatory response. This added tension pulls on the patellar tendon, contributing to your knee pain.

Setup: You can do this on the floor against a wall, a weights bench, or a chair (if the full version is too intense).

Step-by-step:

Place your knee right into the corner of the wall or bench, as far back as feels comfortable.
Bring your other leg up into a high kneeling position.
Squeeze your glutes to keep your hip in a good position.
Extend your hips forward as far as you feel comfortable - imagine a rod through your hips, keeping your back straight (do not arch through your lower back).
You should feel a stretch at the front of your hip and down through the front of your thigh.
PNF contract-relax technique: Once you feel the tightness, tense the muscles for 5-10 seconds (you may need to push your foot back into the surface to create tension). Then relax. The tissue should give, allowing you to sink deeper into the stretch.
Repeat this process until you stop making progress.

Important safety notes:

If your knee feels sore in this position, place a pillow or cushion underneath it.
If done correctly, the pressure should be on your thigh just above your knee, not on the kneecap itself.
You should be able to breathe and talk. If the stretch is so intense that you cannot breathe, you have gone too far.

Re-test again: After completing the couch stretch, immediately re-test the same movement (squats, stairs, running). Has your knee pain changed further?

"Just holding a stretch doesn't work the way that we want it to. You have got to get active. This is the best way to stretch any muscle tissue."

The sitting connection: why your posture matters

You have now identified that releasing your lower back and stretching your quad can change your knee pain. But if you do not address why your back became dysfunctional in the first place, the pain will likely return.

Clinically, the most common cause of this hidden lower back dysfunction is prolonged sitting in poor postures. Sitting at a desk, on the couch, or in the car - if you are consistently sinking or slouching through the exact part of your back that you found was restricted, you are loading that spinal segment day after day.

Over time, that spinal segment can become stiff, tight, and overloaded. This changes the neural tension and mechanical load on your knee, and running can exposes things.

What you can do:

If you do not have to sit, do not sit. Stand, move, change positions frequently.
If you must sit, be in the best position possible. Support your lower back with a rolled towel or cushion.
Take frequent breaks - stand up and move every 30-45 minutes.
Consider a standing desk or alternating between sitting and standing.

From my clinical experience

In 20 years of practice, I have seen countless runners with knee pain who have been told to stop running, ice their knee, and strengthen their quad. They do all of that, and the pain still comes back. Why? Because no one looked at their back.

Your runner's knee is more than likely a consequence of something else. Yes, that part of your knee has become sore and tender. It is very real, very specific, and very valid. But if we only look at your knee, we may miss the bigger picture.

Running is not only normal, it's fantastic for you. It is not the enemy here. The enemy is often the hidden dysfunction you have taken into running - often from hours of sitting in less-than-perfect postures during your non-athletic moments.

If you try these exercises and your knee pain changes, you have proven that your back is involved. Now you need to address both the symptoms (the knee) and the cause (the back).