Runner’s Knee: Symptoms, Causes and Research-Backed Treatment Solutions for Patellofemoral Pain Syndrome
Patellofemoral pain syndrome, sometimes also called “runner’s knee,” is the most common of all running ailments, accounting for 16.5% of injuries according to one recent study.
It’s characterized by a dull pain that is “behind” or “around” the top of the kneecap. Typical aggravating motions include squatting, running (especially downhill), descending stairs, and prolonged sitting.
If you have patellofemoral pain syndrome (PFPS), you will also likely have pain when resisting leg extension, and possibly tenderness if you push against the kneecap itself.
It is important to distinguish PFPS from patellar tendonitis, which is an entirely different injury with a different treatment—patellar tendonitis manifests as pain into the tendon that connects the kneecap to your shin, the patellar tendon.
Patellofemoral pain syndrome is more common among women, though the reasons are not entirely clear.
The oft-cited “Q-angle” theory, which claims that women are more prone to knee injuries because they have wider hips, has been shown to be false.
Additional commonly-cited theories like leg length discrepancies and pronation are similarly unhelpful.
Patellofemoral pain syndrome gets its name from the relevant anatomy around the knee: the cause of the pain is the kneecap—the patella—rubbing against the groove in the femur, where it slides back and forth when you flex and extend the knee.
Causes of runner’s knee
Historically, research on PFPS focused on factors that affected the motion of the kneecap, particularly how the quadriceps control how the patella “tracks” in the femoral groove. Indeed, scientific research has showed that people with poor quadriceps and calf flexibility, poor vertical jumping ability (which is highly dependent on your quads), and weak quadriceps are all risk factors for PFPS.
Blame was often ascribed to a small muscle on the outside of your thigh, called the VMO, which seems to fire differently in people with PFPS. And runners who did exercises that were designed to target the VMO often recovered! But recent research has demonstrated that these gains were probably from improvement in general quad strength, not VMO activation. And unfortunately, many runners don’t find relief from doing only quad strength.
Research backed treatment options for runner’s knee
Fortunately, research in the last ten years has uncovered another mechanism that contributes to knee injuries in runners: hip mechanics.
It turns out that, while it appears that the kneecap “tracks” towards the outside of your leg during squatting and running motions, it’s actually the femur rotating underneath the kneecap This surprising fact perhaps explains why many runners (particularly women) with patellofemoral pain syndrome have weak hip abductors and external rotators. This seems to contribute to altered biomechanics when they run. Because of their muscular weaknesses, their knee “collapses” towards the center of their body when they run. Some work has focused on directly altering the biomechanics of runners with patellofemoral pain syndrome by using a treadmill and camera system to provide gait analysis in real-time.
Unfortunately, this is not an option that’s widely available to most runners. Fortunately, some preliminary research has shown very good results from hip strengthening protocols. Specifically, the literature demonstrates that a successful program should definitely incorporate hip abductor, external rotator, and quadriceps strength.
Many programs that have produced good results also include hip flexor/extensor strength, closed-chain “functional” exercises like squats, and balance training.
Our hip strengthening for runners routine (called Bia), which can be sampled here, and our preventive routines available in our strength training for runners program incorporate these functional and balance exercises gleaned from the research to help keep you healthy.
Other possible treatment options
For most runners, a dedicated strength program will be what ultimately provides relief from patellofemoral pain. But as usual, there are other treatments that can either provide temporary relief or act as a supplement to your strength training. Stretching and foam rolling can be a great adjunct to strength training and can loosen up tight calves and quads. Often, running on an injury will leave you with tight and stiff muscles, which a foam roller and some quad stretching can loosen up. Just take care not to stretch if it irritates your knee.
Applying tape, using either rigid athletic tape in a patellar taping, or with a flexible kinesiology tape, has been shown to provide some relief to athletes with patellofemoral pain.
Some research has also indicated that knee braces (cho-pat straps, neoprene sleeves, and similar devices) may also provide some relief. It seems that the mere presence of the tape or the brace, which provides some tactile feedback on the skin, provides most or all of the relief, not so much the way in which it is applied or the mechanics of how it affects the knee. So a loose “improper” taping helps just as much as a tight, correct taping!
For this reason, I lean towards recommending flexible tapes (Kinesio tape and similar brands) as opposed to rigid tape or braces, since they stay on longer and are less likely to get irritated while out on a run. However, if you get relief from a knee brace or strap, go ahead and use it.
Custom orthotics may speed the pace of your recovery, but at least according to one study, they don’t appear to exert much of an influence after several weeks of rehab. This obscures the fact that many runners have found significant relief from custom orthotics (though others have not), so you may consider them if first-line treatments are not working for you. But given that there is little or no evidence that factors below the knee (i.e. the feet and ankles) play a role in the development of PFPS, custom or even over-the-counter orthotics should not be your first choice in treating patellofemoral pain syndrome.
Outline of conservative treatment:
1. Hip and quadriceps strength exercises:
- Abductors—lying side leg lift or band abduction
- External rotators—lying “clam” or band external rotation
- Quadriceps—straight leg lift
A good starting place is 15 of each, once per day. As your strength improves, you can move to two or even three sets of 15 each. All exercises must be done SLOWLY!
2. General lower leg strengthening and balance
- Balance, possibly on unstable surface (foam pad, bosu ball)—start with 30sec or 1min, build as much as you like
- Mini-squats on a step, starting around 15 repeats and working to two or three sets
- Glute bridge—start with 10-12 10-second holds, build toward 2min continuous
3. Icing after each run
4. Quadriceps and calf stretching.
5. Quadriceps and calf foam rolling
6. Patellar taping, either with traditional athletic tape or flexible kinesiology tape
These options are often more expensive or difficult to obtain and should be reserved for cases of PFPS that don’t improve despite several weeks of strength work, rest, and other rehab.
1. Gait analysis at a physical therapy office equipped with a treadmill and a high speed camera to detect and correct gait abnormalities
2. Custom orthotics may alter your gait and relieve stress on your knee, but it is also possible that they may not help at all.
Return to Running
Patellofemoral pain is notorious for sticking around for weeks or even months, so do be cautious with this injury. In general, you don’t want to run through pain. Sometimes, as you are recovering, your knee may feel a bit stiff at the beginning of a run, but as long as it gets better, not worse, as you progress in your run, you are probably okay to keep going.
It’s difficult or impossible to predict how much time off you’ll need, especially considering the biomechanical roots of this injury. Most treatment plans that are published in scientific journals consist of 4-6 weeks of exercise and no aggravating activities (including running), but all cases of an injury are different. You may only need a few days off if you catch it early, but if you’ve been running on PFPS for a while, you may need a lot longer. A good doctor or physical therapist can often give you a decent estimate of how long it will take you to return to running.
In the meantime, you should stick to cross-training activities that don’t hurt your knee. Aqua-jogging, biking, and using the elliptical are all options, but you’ll have to see how these affect your knee. If a cross training activity hurts your knee, you shouldn’t be doing it!
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