Running is one of the simplest ways to stay fit. You put your shoes on, head outside and start moving.
So why does something that feels so natural sometimes leave you with a sore knee?
Knee pain is one of the more common problems we see in runners, particularly when training volume, intensity or frequency changes. But there isn’t one single reason why a runner develops knee pain.
Sometimes it is a training-load issue. Sometimes it is related to strength, movement or running mechanics. Sometimes hills, terrain or footwear play a role. And sometimes several factors come together at once.
The important thing is that knee pain doesn’t automatically mean you’ve damaged your knee.
In this article, we’ll work through some of the more common reasons runners develop knee pain, what the pain may be telling you, and what you can do about it.
Where Does Your Knee Hurt?
Before we start talking about causes, it is useful to understand where the pain is coming from.
The location and behaviour of your symptoms can give us useful clues.
For example:
- Pain around or behind the kneecap may be consistent with patellofemoral pain.
- Pain around the tendon below the kneecap may point toward patellar tendon-related pain.
- Pain on the outside of the knee can sometimes be associated with lateral knee structures, including the iliotibial band region.
- Pain along the inside of the knee can have several possible causes and needs to be assessed in context.
- Pain associated with swelling, locking or giving way may require a more thorough assessment.
This is why simply saying “my knee hurts when I run” isn’t quite enough information to determine what is happening.
The location, timing, behaviour and response to load all matter.
The Most Common Cause? Your Training Load May Have Changed
One of the first things I want to know when a runner presents with knee pain is:
“What changed?”
Did you suddenly increase your mileage?
Did you start running more hills?
Did you add another session to the week?
Did you start running faster?
Did you enter a race?
Did you come back from a break and immediately try to return to your previous level?
These questions matter because tissues adapt to the loads placed upon them.
We’ve previously discussed this in our running injury series: injury risk isn’t simply about how much you run. It’s also about how much stress that running represents for your individual capacity.
Two runners can complete the same 10 km run but experience very different levels of internal load.
One may finish feeling relatively comfortable.
The other may be exhausted and take several days to recover.
So when a knee starts hurting, don’t automatically blame the distance.
Ask:
What has changed recently?
Common training-load mistakes include:
- suddenly increasing weekly mileage
- adding hills
- increasing running speed
- adding extra sessions
- running hard too frequently
- returning to running too quickly after a break
- doing a long run that represents a large proportion of your weekly volume
- trying to “make up” missed training
- increasing several variables at once
A runner who normally completes 20 km per week and suddenly starts doing 35 km hasn’t simply added 15 km.
They have changed the stress placed on their body considerably.
And if the tissues haven’t had time to adapt, symptoms can develop.
1. Patellofemoral Pain — The Classic “Runner’s Knee”
One of the conditions commonly associated with pain around or behind the kneecap is patellofemoral pain (PFP).
It is sometimes referred to as “runner’s knee” or anterior knee pain.
Patellofemoral pain commonly presents with pain around the kneecap during activities such as running, squatting and using stairs. It is particularly common in physically active people.
A runner might describe it as:
“It feels like it’s underneath my kneecap.”
Or:
“My knee hurts after I’ve been running for a while.”
Or:
“Stairs have started bothering me as well.”
There isn’t necessarily one single structure responsible.
Patellofemoral pain is better understood as a condition influenced by a combination of factors, including load, strength, movement and individual characteristics.
This is important because it changes how we approach treatment.
Rather than simply saying:
“Your kneecap is tracking incorrectly.”
we need to consider the whole picture.
What can contribute?
Potential contributing factors can include:
- a sudden change in training load
- reduced capacity of the quadriceps or hip musculature
- reduced tolerance to repeated knee loading
- changes in running volume or intensity
- fatigue
- movement and neuromuscular factors
- previous injury
- changes in training surface or terrain
This doesn’t mean that one of these factors is automatically the cause.
It means they may contribute to the overall load experienced by the knee.
2. Your Knee May Simply Be Doing More Than It Is Used To
This is one of the most important concepts in running injuries.
Your body doesn’t know that you’ve entered a half marathon.
It responds to the load you give it.
If you have been running 5 km twice a week and suddenly decide you’re going to train for a half marathon, your cardiovascular system may improve relatively quickly.
You might feel fitter.
You might even feel like you could run much further.
But your musculoskeletal tissues need time to adapt to the increased loading.
This is something we discussed in our previous runner’s injury series: cardiovascular fitness can improve faster than musculoskeletal tissue capacity.
So you can feel fit enough to run further before your knee is actually prepared to tolerate the additional workload.
That’s one reason why “I felt fit enough” isn’t necessarily a good measure of whether you’re ready to increase your training.
3. Hills Can Change the Game
Flat running and hill running aren’t exactly the same activity.
Adding hills changes the demands placed on your body.
Uphill running can increase muscular demands.
Downhill running introduces different braking and loading requirements.
So if your normal route is relatively flat and you suddenly start doing several kilometres of hills, you’ve changed your training load even if your total mileage hasn’t changed very much.
This is one reason we need to look beyond the number on your GPS watch.
20 km isn’t always just 20 km.
The terrain, pace, elevation, duration, frequency and your individual response all contribute to the overall training stress.
4. Running Mechanics Can Matter — But They’re Not the Whole Story
Running technique is often blamed when someone develops knee pain.
You’ll hear things like:
“You’re overstriding.”
“Your knees are collapsing in.”
“Your cadence is too low.”
“Your hips are weak.”
These factors can sometimes be relevant.
But we need to be careful about assuming that an unusual movement pattern automatically equals an injury.
Human beings don’t all run exactly the same way.
There is no single perfect running technique that every runner needs to reproduce.
Instead, we want to understand whether a particular movement strategy is contributing to excessive or poorly tolerated load for that individual runner.
For example, fatigue can alter running mechanics.
As we’ve discussed previously, fatigued runners may demonstrate changes such as:
- increased overstriding
- reduced cadence
- reduced neuromuscular control
- changes in hip control
- reduced force production
These changes may alter how loads are distributed through the lower limb.
So rather than asking:
“Is my running technique wrong?”
a better question is:
“Is my current running strategy appropriate for the demands I’m placing on my body?”
That’s a much more useful question.
5. Strength and Capacity Matter
Running is a repetitive activity.
Every stride places load through your lower limb.
Your muscles need to produce and absorb force repeatedly, often thousands of times during a longer run.
This means strength matters.
But strength isn’t just about being able to lift a heavy weight once.
For a runner, we also care about capacity.
Can you:
- produce force?
- absorb force?
- control your body on one leg?
- repeat that movement hundreds or thousands of times?
- maintain control when fatigued?
A runner may have enough strength to perform ten good single-leg squats.
But what happens after 30 minutes of running?
Or after 10 km?
Or during the final kilometres of a half marathon?
This is where strength, endurance and running-specific capacity overlap.
6. Recovery Could Be the Missing Piece
Sometimes the training itself isn’t necessarily unreasonable.
The problem is that there isn’t enough recovery between sessions.
Training creates stress.
Adaptation occurs when the body has enough opportunity to recover from that stress.
So when someone tells me:
“I’ve only increased my running a little bit, but my knee has started hurting.”
I also want to know about:
- sleep
- work or study stress
- gym training
- other sports
- previous training
- recent illness
- rest days
- overall weekly activity
Your running load doesn’t exist in isolation.
A runner who completes three easy runs but also plays two games of netball and performs three heavy gym sessions has a very different overall training week from someone who only runs three times.
All activity creates stress on the body.
This is one of the important lessons from our previous discussion of internal and external load.
7. Your Shoes Might Not Be the Main Problem
Footwear is an easy thing to blame when knee pain develops.
And yes, footwear can be relevant.
But changing shoes isn’t automatically the solution.
A new pair of shoes often gets blamed because the timing makes sense:
“I bought these shoes two weeks ago and now my knee hurts.”
But correlation doesn’t necessarily mean causation.
At the same time, changing footwear can represent a change in your running exposure, particularly if the new shoes feel substantially different from what you’re accustomed to.
So footwear should be considered as one part of the assessment, rather than automatically being labelled as the cause.
8. What About Running Surface?
The same principle applies to running surfaces.
Concrete, bitumen, grass, trails and treadmills all provide slightly different running environments.
But the idea that one surface is simply “good” and another is “bad” is too simplistic.
What matters is how your body responds to the particular loading environment.
A sudden switch from flat road running to uneven trails, for example, can introduce:
- different terrain
- elevation changes
- different footing
- more frequent changes of direction
- different muscular demands
Again, it’s not necessarily the surface itself.
It may be the change in exposure.
So, Should You Stop Running?
This is probably the question most runners actually want answered.
“My knee hurts. Do I need to stop?”
Sometimes yes.
Sometimes no.
It depends on the nature and severity of the symptoms.
For some running-related conditions, continuing with appropriately modified activity can form part of rehabilitation. Current evidence around patellofemoral pain supports education and exercise-based management, with treatment tailored to the individual rather than simply relying on rest.
The important word here is modified.
You might need to temporarily change:
- distance
- speed
- hills
- frequency
- recovery between sessions
For example, a runner who normally completes 10 km may temporarily tolerate 5 km much better.
Another runner may find that reducing intensity is more useful than reducing distance.
This is why there isn’t a universal “safe distance” for everyone with knee pain.
A Simple Example
Let’s meet Sarah.
Sarah normally runs three times per week:
- Tuesday: 5 km easy
- Thursday: 5 km intervals
- Sunday: 8 km long run
Her total is around 18 km per week.
She decides to enter a half marathon.
Over the next six weeks, she starts adding extra kilometres to her long run.
She also starts doing hill sessions because she wants to prepare for the course.
Her weekly volume increases.
Her intensity increases.
Her terrain changes.
Her Sunday run becomes much longer.
Then her knee starts hurting around the 7 km mark.
Sarah’s first thought is:
“I need new running shoes.”
But if we look at the whole picture, the shoes may not be the most important thing that changed.
Her training load has changed considerably.
The problem isn’t necessarily that running is bad for her knee.
The problem may be that she has increased the demand faster than her current capacity can accommodate.
The solution may therefore involve modifying the training load while rebuilding the capacity required to reach her half-marathon goal.
That’s a very different approach from simply telling her to stop running.
What Can You Do If Your Knee Hurts When Running?
The first step is to work out what has changed.
Look back over the previous few weeks.
Ask yourself:
Training
- Have I increased my mileage?
- Have I added another running day?
- Have I started running faster?
- Have I introduced hills?
- Have I increased my long run?
Recovery
- Am I sleeping enough?
- Have I had more stress than usual?
- Have I added another sport?
- Have I increased gym training?
Symptoms
- When does the pain start?
- Does it get worse as I continue?
- How does it feel later that day?
- How does it feel the next morning?
- Is the overall trend improving or worsening?
Capacity
- Have I been consistent with strength training?
- Can I perform single-leg movements comfortably?
- Can I tolerate hopping or running progression?
- Has my training base been consistent?
This information is often much more useful than simply asking:
“Where exactly does it hurt?”
When Should You Get Your Knee Assessed?
Not every sore knee requires urgent medical attention.
But there are situations where getting assessed is sensible, particularly if:
- pain is persistent or worsening
- swelling develops
- your knee repeatedly gives way
- your knee locks
- you cannot comfortably bear weight
- symptoms started after significant trauma
- your running performance is progressively deteriorating
- symptoms aren’t improving despite sensible training modification
A sports physiotherapy assessment can help determine whether the main contributors are related to training load, strength and capacity, movement, the environment, equipment or another factor.
The goal isn’t simply to identify where it hurts.
It is to understand why it hurts and what your knee currently has the capacity to tolerate.
How Is Running Knee Pain Treated?
This depends entirely on the diagnosis and the individual.
But treatment commonly involves some combination of:
Load management
Adjusting training so that the knee is exposed to an appropriate amount of stress while capacity is rebuilt.
Strength and conditioning
Progressively improving the capacity of the muscles and tissues involved.
Running modification
Changing variables such as pace, volume, frequency or terrain where appropriate.
Movement and technique
Assessing whether particular movement strategies are contributing to the problem.
Gradual return to running
Progressively increasing exposure rather than jumping immediately back to previous training volumes.
Education
Understanding what is happening is part of rehabilitation.
For patellofemoral pain specifically, evidence supports exercise-based approaches combined with education, with treatment tailored to the individual’s presentation.
The aim isn’t simply:
“Make the pain disappear.”
The aim is to build enough capacity to tolerate the running you want to do.
The Big Take-Away
Most runners don’t develop knee pain because running is inherently bad for their knees.
More often, the problem is a mismatch between the load being applied and the capacity available to tolerate it.
That mismatch can come from:
- too much too soon
- inconsistent training
- increased intensity
- hills or terrain changes
- inadequate recovery
- insufficient strength or capacity
- previous injury
- multiple training stresses occurring at once
And sometimes, there is more than one factor involved.
So the next time your knee hurts after running, don’t immediately ask:
“What’s wrong with my knee?”
Also ask:
“What’s changed?”
That question can tell us a lot.
Key Take-Aways
Knee pain doesn’t automatically mean you’ve damaged your knee. Pain can arise from a number of different factors and needs to be considered in context.
Look at your training load. Changes in mileage, intensity, frequency, hills and long-run distance can all alter the stress placed on your body.
Don’t blame running technique too quickly. Movement patterns can be relevant, but an unusual technique doesn’t automatically mean something is wrong.
Build capacity. Strength, endurance and the ability to repeatedly absorb and produce force are important for runners.
Recovery matters. Running is only one part of your total weekly load.
Don’t automatically stop everything. In some conditions, appropriately modified running can form part of rehabilitation, but the right approach depends on the individual presentation.
Think beyond the pain. The goal is not just to make the knee feel better. The goal is to build the capacity needed to return to the running you enjoy.
FAQ
Q1: Is running bad for your knees?
Not necessarily. Running is a form of loading, and healthy tissues can adapt to appropriately progressed loads. Problems can arise when the demands placed on the body exceed its current capacity.
Q2: Why does my knee hurt only after I run?
Symptoms that appear after running can be influenced by the amount and intensity of load accumulated during the session. The timing of symptoms, your recent training history and how your knee responds over the following hours and days can all provide useful information.
Q3: Should I stop running if my knee hurts?
Not automatically. Depending on the cause and severity of the symptoms, modifying your running load may be appropriate. However, persistent, worsening or significant symptoms should be assessed rather than simply pushed through.
Q4: What is runner’s knee?
“Runner’s knee” is commonly used to describe patellofemoral pain, which typically involves pain around or behind the kneecap and can be aggravated by activities such as running, squatting and stairs.
Q5: Can weak muscles cause knee pain when running?
Reduced strength or capacity can be one contributing factor, but knee pain is rarely explained by a single factor in isolation. Training load, previous injury, movement, recovery and other individual factors may also contribute.
Q6: Should I change my running shoes if my knee hurts?
Not necessarily. Footwear can be one factor worth considering, particularly if you’ve recently changed shoes, but changing footwear alone isn’t a guaranteed solution. Your training load and overall running exposure should also be considered.
Q7: How can a sports physiotherapist help with running knee pain?
A sports physiotherapist can assess your symptoms, training history, strength, movement and running-related loads to identify factors that may be contributing to your pain. They can then help develop an appropriate rehabilitation and return-to-running plan.
If your knee pain is stopping you from running, or you’re unsure how to modify your training while it settles, a sports physiotherapy assessment can help identify what is contributing to your symptoms and develop a plan to get you back to running.
If you need help with recovery from a running injury or need assistance building a safe training plan? Book your running assessment now via the bookings page.
See you in the Clinic
Chris Dillon
Chris Dillon is a titled APA Sport and Exercise Physiotherapist and the founder of Brisbane Sports Physiotherapy. He works with athletes from grass roots to the elite level with a focus on injury prevention and load management. He is a member of the Australian Physiotherapy Association (APA) and registered healthcare provider with the national body AHPRA.