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What is runner’s knee?
Runner’s knee is the common name for patellofemoral pain syndrome. It refers to pain felt in and around the kneecap. It’s usually caused by one or more of the structures in the patellofemoral joint becoming inflamed or irritated.
Runner’s knee is perhaps not the best name for this condition. You can get patellofemoral or kneecap pain from many activities, not only running.
What's the patellofemoral joint?
Your knee actually consists of 2 joints. First, you have the main knee joint formed between the bottom end of your thigh bone (femur) and the top end of your shin bone (tibia).
Then there’s the smaller joint (patellofemoral joint) over the front of your knee, where the underside (back) of your kneecap lies over the front of your shin and thigh bone.
The kneecap sits inside the tendon that attaches your front thigh muscles (quads or quadriceps) to your shin bone. It moves in a shallow groove that runs across the front of your main knee joint.
Both the underside of the kneecap and the groove are lined with slippery cartilage. This cartilage protects the bones.
The patellofemoral joint is held together by a thick capsule with a synovial lining made up of cells that “look after the joint.” These cells have several tasks, but the main ones include producing nutrients for the joint and kick-starting inflammation when it’s needed.
When you have runner’s knee, any or all of these components that make up the patellofemoral joint can be injured.
Runner's knee symptoms
We’ve listed the most common symptoms below. But, of course, every person’s injury is slightly different, and you will likely not experience all of these symptoms.
- People who have runner’s knee will feel pain in or around the kneecap.
- The pain is usually relatively diffuse, and you can’t really find it when you try and press around your knee.
- Activities that load the knee joint (like walking up or downstairs or hills, squatting, running, or jumping) often cause pain.
- Sitting still for long periods with your knee in a flexed position may hurt.
- You may notice a little bit of swelling or puffiness either above or below the kneecap.
- The kneecap may clunk, click or crackle when it moves, but this can also happen in uninjured knees.
- The pain usually starts gradually or without any traumatic event.
Runner’s knee doesn’t show up on scans. If you have pain over the front of your knee and your MRI scan didn’t show any injuries, you likely have runner’s knee.
What causes Runner’s knee?
Runner’s knee is an overload injury that develops when the forces you place on your patellofemoral joint are higher than what it can cope with. This overload can happen suddenly, during one session, or gradually accumulate over several sessions.
There are several different reasons or ways in which you can overload your kneecap. For this article, we’ve divided them into 4 categories:
- Training errors
- Poor biomechanics
- Weak thigh muscles
- Daily activities
The two most common training errors that can lead to runners developing this injury are:
1. If a training session is too hard
At any given time, your body (and your knee) will have a specific strength or capacity for how much load or force it can handle.
This strength can increase when you train or decrease when you stop being active or don’t exercise for a while.
If you do a training session that is much harder (faster, further, more hilly, etc.) than what you’re used to, your knee may not be strong enough to cope with those high loads.
2. If you don’t allow enough recovery time between sessions
Whenever we exercise, our bodies sustain micro-damage. This is normal and also the reason why you need to allow enough recovery time after training sessions. The body uses this recovery time to repair the micro-damage and grow stronger.
On the other hand, if you don’t allow enough recovery time, the micro-damage accumulates and causes overuse injuries like runner’s knee.
Biomechanics refers to how your leg moves when you walk, run or jump. Nobody’s legs move in an absolutely straight line. Instead, there is a vast range of movement patterns that are seen as typical. Researchers have identified 2 biomechanical factors that may predispose you to develop runner’s knee:
- If your leg turns in excessively and/or
- If your leg crosses over too far towards the mid-line.
Why is this a problem? As mentioned earlier, the kneecap moves in a shallow groove over the front of the knee.
If your knee turns in excessively or your leg moves too far over to the midline, it can cause the kneecap to be pulled slightly out of alignment. This can put more force on specific parts of your joint than it should, causing it to strain.
The main causes for poor biomechanics when you run include:
- Weak muscles – especially the core, gluteal, and ankle stabilizing muscles
- Poor balance / position sense
- Reduced ankle dorsiflexion due to a stiff ankle joint or tight calf muscles
- Tight thigh muscles (especially outside thigh muscles) can also pull the kneecap out of alignment
- Unsupportive or too flexible shoes
- Sometimes running with poor form or biomechanics can simply be a bad habit
The Exakt Health app includes an exercise treatment plan for runner’s knee, designed to address all of these elements.
Weak quadriceps (thigh muscles)
Your thigh muscles are meant to absorb a large portion of the force created when you run. Therefore, if they are weak, more of this force is transferred to your knee joints.
Running isn’t always the main reason why people develop runner’s knee. Sometimes they irritate the kneecap through other activities they do in the day, and then running just compounds the injury. Examples include:
- Activities that involve a lot of repetitive deep squatting
- Kneeling for long periods
- Going up and down the stairs several times while carrying extra weight like boxes
How long does runner's knee last?
How long it takes to recover from runner’s knee depends on how severe your specific case is and how quickly and effectively you treat it.
You usually start seeing promising improvements in symptoms within 4 weeks of starting the right treatment plan.
Mild cases can fully resolve within 6 to 8 weeks, while more severe cases may take several months to recover. Especially if you’ve ignored it for some time and continued to train through pain.
Can runner's knee cause permanent damage?
Yes, some evidence suggests that if you neglect runner’s knee, it may predispose you to develop osteoarthritis in your patellofemoral joints.
But this is not true for everyone, so please don’t worry about this too much!
Think of it as a good reason not to ignore your knee pain and instead seek treatment advice early.
How to solve runner's knee
The research currently shows that the most successful treatment for runner’s knee combines the following 3 elements:
- Relative rest
- Exercise therapy
- Running retraining
To allow your injured knee to settle down and recover, you will have to adjust your training load. Relative rest is different from complete rest. You don’t have to stop all your activities. You only need to modify their volume, intensity, or the type of activity you do.
You may, for instance, find that if you run shorter distances or avoid hills, you can do so without making your knee pain worse. Some adjustments that may help include:
- Reducing your number of weekly training sessions
- Sticking to low-intensity training (only easy runs)
- Reducing your running distance
- Avoiding hilly or uneven running surfaces
Suppose you’ve made these adjustments, and your knee still feels sorer after a run. In that case, you may have to switch out running for other activities (like walking) that don’t irritate it.
In another article, we’ll discuss what exercises you should do in more detail because your treatment plan and exercises should adjust as your knee recovers.
The research shows that a rehab plan that combines exercises that work on core, hip, and thigh strength and control appears to be most effective for treating runner’s knee.
We’ve designed the runner’s knee treatment plan in the Exakt Health app with this research in mind. It uses your feedback to adjust the exercise intensities as your knee recovers. You can download it for free from the app store.
Researchers found that restoring your strength and control in your legs and doing all the right exercises doesn’t always lead to improvements in running style. So, you may continue running with the same running style that contributed to you developing runner’s knee in the first place.
There are some easy adjustments and drills that you can do to improve your running style, and we’ll discuss these in detail in future articles.
The three treatment elements discussed above are the most important things to get right, but other things might also help.
For example, orthotics, massage, taping, dry needling, and acupuncture have all been shown to help provide short-term pain relief for runner’s knee.
According to the research, electrotherapy modalities like ultrasound and laser are a waste of time and not worth using for this injury.
Runner’s knee is a common condition that can get in the way of your sport and daily life, but there are many things you can do to help it.
Always start by giving your knee the rest it needs, then build up the appropriate exercises and work on improving your running style.
Need help going through the stages of runner’s knee rehab? We have it all laid out for you. Download the Exakt Health app to get started!
- Brukner, P., Khan, K., & Brukner, P. (2018). Brukner & Khan’s clinical sports medicine. Sydney: McGraw-Hill.
- Collins, N. J., et al. (2018). “2018 Consensus statement on exercise therapy and physical interventions (orthoses, taping and manual therapy) to treat patellofemoral pain: recommendations from the 5th International Patellofemoral Pain Research Retreat, Gold Coast, Australia, 2017.” Br J Sports Med 52(18): 1170-1178.
- Crossley KM. Is patellofemoral osteoarthritis a common sequela of patellofemoral pain? Br J Sports Med. 2014 Mar;48(6):409-10. doi: 10.1136/bjsports-2014-093445. PMID: 24569144.
- Lack, S., et al. (2018). “How to manage patellofemoral pain – Understanding the multifactorial nature and treatment options.” Physical Therapy in Sport 32: 155-166.
- Neal, B. S. (2019). The influence of lower limb biomechanics on the development, persistence and management of patellofemoral pain in recreational runners, Queen Mary University of London.