Runner’s Knee: The What, How, and Why of Treating Patellofemoral Pain Syndrome

Do you run?

Do you have knees?

Then, arguably, you have runner’s knees.

Bad jokes aside, runner’s knee is an all-too-common condition that is estimated to make up 17% of all running injuries. That qualifies it to be the #1 injury affecting runners, with IT Band Syndrome coming in second.

Runner’s knee can manifest in a variety of different ways, but the most common symptom is pain under and around the kneecap. This hallmark pain gives the condition it’s official name: Patellofemoral Pain Syndrome, or PFPS.

Up to 80% of runners are injured each year, and with runner’s knee making up seventeen percent of that, the math says that approximately 1 in 4 runners will experience PFPS in a given year.  

With numbers that high, it’s important to understand what PFPS is, what to look out for, and when to seek treatment in order to keep yourself healthy and on the trails (or the track or the road).

What is Runner’s Knee?

So, if the condition is that common, what exactly is runner’s knee? And why is it so prevalent among runners?

Common Symptoms

The first cue that something’s not right is lingering pain around the knee cap during or following a run. The pain might move around to above, below, or underneath the knee cap, and may become worse with longer distances or running hills.

After finishing a run, there is often diffuse pain that is difficult to pinpoint – even when touching the tissues surrounding the joints. It is common for individuals with patellofemoral pain to say the pain is “underneath the knee.”

Other movements that are likely to create the same irritating knee pain include squatting, climbing up or down stairs, and walking up or downhill. Sitting or lying still for long periods of time may cause stiffness and aching in the knee.

Anatomical Breakdown

The patellofemoral joint is a created by the patella (knee cap) moving on the trochlear groove at the end of the femur (thigh bone). The trochlear groove is an indent in the bone that “holds” the patella in place. This creates the patellofemoral joint.

The quadriceps muscles connect to the upper edge of the patella via the quadriceps tendon. At the lower edge of the patella, the patellar tendon (or patellar ligament; they are the same thing) anchors it to the top of the tibia (shin bone). As the quadriceps contracts and relaxes, the patella moves up and down the femur. This is normal.

Problems arise when the bony surfaces of the patellofemoral joint begin to degrade from continuous rubbing.  What causes this rubbing and degradation?  Basically, the knee acts like a hinge as it bends and extends.  A hinge is designed for movement in one plane of motion – and so is your knee.  When the knee moves too far inward or outward during running, it causes poor tracking and alignment of the patella on the femur.  This abnormal movement increases joint compression and degradation of the cartilage and bone under the knee cap.

Repetitive actions like running with poor patellar tracking causes abnormal loading and degradation of the joint.  So then, what is cause of the poor alignment?

What Causes Runner’s Knee?

Surprisingly, runner’s knee is not a true knee problem, but rather, a hip problem that manifests pain at the knee cap. 

It’s often assumed that the patella is moving out of alignment, but that’s a common misconception. Based on functional MRI records taken, it’s actually the femur that moves out of alignment “underneath” the patella. This is usually due to a lack of stabilizing muscle activation at the hip during squatting actions like running resulting in poorly controlled action of the femur, though there are other potential causes.

Previously, it was thought that strengthening the quadriceps, and specifically the VMO (vastus medialis obliquus – that muscle bulge on the inside of your knee) part of the quadriceps, it would “re-align” the patella.  Although adequate quadriceps strength is important for treating patellofemoral pain, studies point to gluteal activation and strengthening as the key to solving pain from runner’s knee for good.

Contributing factors for PFPS can be both intrinsic and extrinsic to the hip and knee joint. These may include:

How is Runner’s Knee Treated?

Ask multiple practitioners this question and you’ll annoyingly get different, and often contradictory, answers.  Even a quick Google search will yield far too many results, and most will advise the exact thing you don’t want to do … stop running.

Initially, the focus will be on identifying the biomechanical deviations and repetitive motions that contribute to PFPS. Once symptoms are under control, the focus shifts to retraining movement patterns and combatting any biomechanical deficits that may have caused the pain in the first place.

Strong evidence shows that running based physical therapists can identify and target biomechanical deviations and muscle imbalances that increase joint stressors and contribute to patellofemoral pain. In order to properly address the underlying cause of PFPS, the PT will need to identify movements in recreational or every day activities and running that are aggravating the tissue surrounding the knee.

How is Runner’s Knee Diagnosed?

The physical therapist will utilize both static and dynamic functional tests to identify every day activities and recreational activities that contribute to patellofemoral pain. The PT may ask to observe squatting, sitting, kneeling, walking, and especially running to help determine the cause of injury.  Since there are different biomechanical faults during running that lead to runner’s knee, it’s vital to record slow motion video of your running to highlight these specific deviations.

Furthermore, an evaluation of the back, hips, knees, ankles, and feet are an important part of the therapist’s evaluation to identify discrepancies within the kinetic chain. For example, an individual with scoliosis will create muscle imbalances at the low back that impact the alignment of the hip and functionality of the glutes. In turn, abnormal glute muscle function has been shown to create patellar mal-tracking and poor frontal plane knee control.

Following the functional tests, an assessment of the ROM, strength, stability, flexibility and neuro-activation will be performed. Common abnormalities found in individuals suffering from PFPS include:

Poor patellar tracking can increase joint stress at the knee that accumulates over time and triggers a flare up the knee. Leg length discrepancies may lead to muscular imbalances that impact the entire kinetic chain, which can contribute to other injuries developing. Lastly, crepitus can be felt when the knee cap grinds on the surface of the femur. Crepitus is a grinding sound, like two rocks rubbing together, under your knee cap that alerts you a change needs to be made.  

While those are common symptoms associated with runner’s knee, some patients may not have any of them. A physical therapist will interpret the findings from the physical evaluation, subjective history, and movement analysis to determine the proper diagnosis. The causes of patellofemoral pain are multi-faceted, and it is important to see a healthcare professional to establish a diagnosis rather than self-diagnosing.

What’s the Prognosis?

A recently published research article identified patellofemoral pain as a non-self-limiting injury in adolescent individuals. Non-self-limiting means the injury does NOT go away on its own and special care is warranted to prevent it from recurring in the future or becoming a chronic condition.

With physical therapy, most patients can return to pain-free running and stop the recurrence of patellofemoral pain in 2-4 months. However, depending on the chronicity and severity of the pain, recovery time may take longer. It cannot be stressed enough that early intervention with patellofemoral pain is essential to prevent recurrence and reduce recovery time!

Various research articles showed that the potential for recovery from chronic patellofemoral pain becomes impaired the longer the individual has had the injury. More than 50% of individuals with chronic patellofemoral pain continue to have pain up to 8 years down the road. Waiting to address patellofemoral pain not only prolongs the recovery time, but can lead to other injuries occurring as a result of compensations or imbalances in running form.  

For example, a 5k runner with patellofemoral pain may start to subtly limp with each stride during training.  Over time, the subtle change in running gait may cause the opposite, uninjured leg to deviate inward or absorb more load, and ultimately create overuse that results in injury. This may begin an on-going cycle of further injuries developing due to initial onset of patellofemoral pain. Instead of just having knee pain, the runner may develop lower back, hip, or foot pain as well.

What’s the Treatment Protocol?

Treatment for patellofemoral pain focuses on alleviating the pain and addressing the biomechanical dysfunctions that are aggravating the joint.

Starting out, controlling symptoms to allow you to continue running is key. Pain and swelling will be reduced through compression and soft tissue work. The physical therapist will work on movement retraining and “waking up” muscles that may have become less active in an effort to prevent pain. (Your brain will reduce the signal to muscles in the presence of pain to avoid further injury or tendon overload; this is called autogenic inhibition).

There is some literature to support the use of k-tape to improve symptoms of patellofemoral pain as well. In theory, the tape is supposed to provide mechanical support to promote better patellar tracking. However, the k-tape can’t induce enough force to provide a mechanical change to tracking in the knee joint.  Instead, the stretching of the tape provides a proprioceptive cue to the brain that alerts the body to control movement of the knee. In short, the use of k-tape may be a good tool to reduce pain; however, it won’t make any lasting change in biomechanics.

Although there may be many strategies for alleviating symptoms such as ice, rest, stretching, and knee braces … boring, boring, boring … research is quite clear that one method of treatment in particular can truly solve the cause of patellofemoral pain syndrome.

Gluteal activation, strengthening, and dynamic alignment training is the “gold standard” to fix runner’s knee. 

Pretty odd, right? Treat the hip to fix the knee!  Although massage, stretching, and electrical stimulation around the knee temporarily feels good, it doesn’t result in full recovery.

Since functional MRI studies have shown that it’s the femur moving under the patella and NOT the patella moving over the femur, then fixing poor alignment has to work the tissues that control the rotation and inward/outward movement of the femur.  The two major tissues that control the femur are the gluteus maximus and gluteus medius.

When there is poor gluteal activation, meaning your brain can’t send the proper signals to activate these muscles, and there is weakness, you are unable to control the movement of the femur. This results in increased patellofemoral compression and pain, and one annoyed athlete.

By re-training the neuromuscular connection between the motor cortex of your brain and your gluteal muscles through progressively more challenging and dynamic sports actions, your body will learn proper hip and knee control, allowing the healing to occur. 

Improving double-leg squatting form to favor a more hip-dominant versus knee-dominant movement is key.  This adjustment will queue proper activation of the gluteal muscles, giving you a greater ability to control abnormal motions of the knee.  Once you can control you hip and knee alignment with double-leg drills, you can move into training alignment with single-leg drills.  Ultimately, since running is a single-leg sport, meaning at no point are two legs on the ground at the same time, you’ll need to master single-leg alignment to fully fix runner’s knee.

In addition to neuromuscular alignment training, strength training for the gluteal muscles is essential so the hip can offload forces from the knee during running.  Additionally, running retraining, which is the process of correcting form errors while running, has shown to be a beneficial and long-term treatment strategy.  Running retraining can be as simple as putting a mirror in front of a treadmill and focusing on keeping your knees from coming in towards each other.  Studies have shown that as few as 8 training sessions can decrease runner’s knee pain for up to 3 months post-training.

The purpose of running retraining is to adjust specific components of the running gait to reduce forces that the body must absorb and to improve load distribution throughout the body. Running adaptations include changes to cadence, vertical oscillation (the amount of up -and-down movement), trunk lean, and reducing cross over – just to list a few. Emerging research has shown combining running retraining with strength training to be very promising.

The Big Picture

Patellofemoral Pain Syndrome is all too common within the running community. With 25% of runners experiencing it each year, knowledge about the condition (and prevention) should be more prevalent. Gaining an understanding of sound running mechanics and shoring up any gait inefficiencies will help to keep runner’s knee out of your running career.

If you have knee pain under or around your knee cap, don’t wait for it to go away. The nature of PFPS necessitates intervention to calm symptoms and resolve the contributing biomechanical factors. Seeing a running specialist sooner rather than later can save you a lot of pain, hard work, and rehab time.

Runner's Knee

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