Patellofemoral Pain Syndrome (PFPS) is the most prevalent running-related injury afflicting 19-30% of female runners and 13-25% of male runners.1,2 It is usually characterized by a gradual onset of pain on the front of, or behind the patella (knee cap), while under loading or compressive forces. These forces are present during activities that utilize the combination of significant quadriceps demand with knee flexion (bending). Running is a good example of this scenario as upon landing, you bend your knee and your quadriceps contract in an effort to cushion the landing and then quickly straighten the leg to propel you into your next stride. Running is one such activity than can lead to PFPS, but other activities include cycling, squatting, stair climbing, and even prolonged sitting.3
When the knee bends and straightens, the patella is supposed to glide up and down comfortably in the trochlear groove, which is the groove in the middle portion of the end of your femur (thigh bone) where it meets the patella and tibia (shin bone). PFPS is due to abnormal tracking of the patella in this groove which can be due to many reasons including alignment issues, muscular imbalances or weaknesses, decreased flexibility, patellar hypermobility, running mechanics, and over activity. PFPS is likely caused by several of these factors to varying degrees as each case is very individual. We will get into each of these factors in more detail here and what can be done to address them.
The alignment issues that can lead to PFPS include femoral neck anteversion (inward rotation of thigh bone at the hip), genu valgum (knees tilt inward i.e., knock knees), larger Q angle (wider hips resulting in knees tilting inward relative to hips), knee hyperextension, tibial varum (bow leggedness), and excessive rearfoot pronation (flat feet).4,5 The patella itself can also have alignment issues, differences in shape, and poor congruency with the groove it sits in which can also lead to PFPS.
Muscular imbalances and weakness can also factor into PFPS. One way they are thought to is via quadriceps weakness, specifically the vastus medialis obliquus (VMO) which is the small quadriceps muscle just above and to the inside of your patella. The VMO is overpowered by the structures on the outside of the knee including the iliotibial band (ITB), lateral retinaculum, and vastus lateralis (VL) muscle, causing the patella to be tilted and pulled towards the outside out of the groove leading to increased compression and pain.6 Another way muscular weakness can lead to PFPS is due to weak hip musculature. Decreased hip abductor and external rotator strength can cause the femur to rotate inward and/or knee move inward.7 To use an analogy to make this all a bit clearer is to think of the patella like a train that rides on the tracks of the groove it sits in. If your VMO is too weak and/or the structures on the outside of the knee too tight, the train itself can be pulled off the tracks. If you hip muscles are too weak then your femur and the groove it has on the end of it move and in essence the track moves out from under the train.
Decreased muscular flexibility specifically of the hip flexors and quadriceps can also contribute to increased patellofemoral compression.8-10 This occurs from these muscles pushing the patella down into the groove behind it.11 Tight tensor fascia latae (TFL) muscle and iliotibial (IT) band can pull the patella towards the outside, also causing compression. Tight hamstrings will pull the tibia (shin bone) backwards also causing compression of the patella.12
Poor running mechanics can also lead to development of PFPS. Female runners who have PFPS have been shown to have their hips rotate inward and knees move inward more while running than those without PFPS.13 Male runners with PFPS have more contralateral (opposite side of leg on ground) hip drop while running.14 Runners with a history of PFPS also have higher impact peak and loading rates i.e., they land harder on the ground don’t absorb their landings as well.15
Errors in training account for over 60% of all running-related injuries. Training errors that have been linked to PFPS include increases in running mileage and/or speed, and changes in running environment including hill training.16 Other factors related to training that can lead to such an injury include decreased recovery time, decreased sleep, nutritional deficits, and increased overall stress.17
Now that we have covered the many possible causes of PFPS, lets discuss which treatments have been shown to be effective and not effective. Let’s start with manual therapy techniques which are essentially treatments a clinician, like a physical therapist, would perform with their hands on you, though there are some that can accomplished on your own. Mobilizations are different techniques where a clinician applies forces around a joint to improve movement within the joint capsule itself. Research has shown knee joint mobilizations to be beneficial for decreasing pain due to PFPS as long as it’s done in conjunction with other treatments i.e., mobilizations alone are not enough to make a change.15
Another group of manual therapy techniques are soft tissue techniques, which include massage, myofascial release, ischemic compression of trigger points, and instrument assisted soft tissue mobilization (IASTM). There is some evidence that these techniques can break up connective tissue adhesions, decrease muscle tone, improve blood circulation, and decrease pain, but there is not strong evidence that any of these techniques in isolation are effective in treating PFPS.17That being said, any and all can be effective as part of the overall treatment program. One way to recreate these soft tissue techniques on your own is with foam rolling which has been shown to decrease neuromuscular tone and improve short term flexibility in the muscles you foam roll.18-20 A foam rolling program for endurance athletes is shown in the video below.
Another soft tissue technique is Trigger Point Dry Needling (TPDN) which is a technique performed by clinicians such as physical therapists where they insert a thin needle into trigger points found in muscles to get them to release. Trigger points in the quadriceps muscles, specifically the vastus medialis and rectus femoris can refer pain to the front of the knee which can mimic or exacerbate symptoms of PFPS.21 While anecdotally patients have reported benefits from TPDN to address these trigger points and their PFPS there is not yet research showing significant improvements from it.
Taping the patella is another manual therapy strategy with some evidence for success. McConnell taping (pictured here) specifically, has been proven to be able to pull the patella inward22 and help with VMO activation.23 This can help prevent the patella being pulled to the outside and decrease pain.
Using foot orthotics in running shoes (or any shoe) is another treatment option to help with PFPS. The theory is that if the foot over-pronates (the arch flattens too much or too quickly without control), then the shin and knee can follow resulting in the knee moving inward, contributing to PFPS. While studies are limited linking over-pronation and PFPS, there is evidence of success in treating PFPS with use of orthotics regardless of foot type, at least in the short term.24 Studies have shown greater success in individuals who are older, shorter, lower pain levels to start, increased foot mobility, decreased pain with single squat when wearing orthotic, decreased ankle dorsiflexion (ability to bring toes up toward shin), and shoes with poor motion control.25-27 So to simplify, orthotics could help anyone with PFPS, but if you meet one or more of the above criteria you make have a better chance at success.
As we discussed above, muscular weaknesses can be a contributor to PFPS, thus it would be logical that strengthening exercises would be part of the treatment process. One of those muscles was the VMO muscle of the quadriceps which should pull on the inside of the patella to counteract the pull of the tight structures on the outside of the patella. Exercises that involve the last 10 degrees of knee extension (straightening), also known as terminal knee extension (pictured here), strengthen the VMO. Studies have also shown that electrical stimulation and taping the knee to pull inwards can help with VMO activation as well.28 Weaknesses in the hip must also be addressed, especially hip external rotation and abduction strength. Improvements in these areas can decrease stress on the knee joint.29 Clamshells, side leg raises, lateral step downs, and lateral band walks (all shown in the videos below) are some of the go-to exercises to strengthen these movements.
Muscles that are tight, especially the hip flexors, quadriceps, TFL, and hamstrings, should be addressed in treatment as well, with stretching. Below are the stretches to address these respective muscle groups. Research on how long a particular stretch or the sum of all your stretches of a muscle should be varies widely, but a good goal would be to stretch each muscle or muscle group for a total of at least 60sec per session. This could be 1x60sec, 2x30sec, 3x20sec etc.
Quadriceps:
Hip Flexor:
TFL / IT Band:
Hamstrings:
The last piece of the treatment puzzle is neuromuscular re-education, which is the re-training the connections between your nervous system and muscles to produce better movement patterns. The best example in this context would be to train your knee not to move inwards every time you land during running. While you may have strengthened the muscles to keep your hip from rotating and moving inward, strengthened your VMO to pull your patella inward, increased the pliability and flexibility of your tight muscles, and utilized various other treatments we’ve discussed here, you still need to train your neuromuscular system to create the movement you want. In other words, your body now has been made able to perform these movements, but you still need to train it to perform these movements, as you have likely been moving poorly for a while. Performing some double and single leg jumping activities and eventually running while watching yourself in a mirror can give you a visual cue to when your knee is caving in or not, so you can develop what both feel like, and begin to learn to correct the movement so your knee doesn’t cave in. Research has shown that running in front of a mirror has helped re-train proper running mechanics with carry over for up to 3 months afterwards.30 Also since landing too hard without properly absorbing the impact can lead into increased injury risk including PFPS, using the auditory cue of how loud you land during run can help train you to land softer and thus better absorb your landings.
There are a few treatments that have been shown to not be effective in treatment of PFPS. These are laser, ultrasound and phonophoresis therapies.31 You would most likely only come across them at a clinician’s office, such as a physical therapist though. While some were more popular in the past and/or gaining popularity now, research currently doesn’t support their use for PFPS.
Conclusions
This was a lot of information to absorb, but there are some simple conclusions we can boil things down to. First, you should identify if you truly have PFPS which will present as a gradual onset of pain on the front of or behind the patella while under loading or compressive forces present during activities such as running or cycling. Several overuse injuries can also present this way so a healthcare professional such as an orthopedic doctor or physical therapist can help you identify your injury as PFPS. As a quick disclaimer, most of the treatments discussed here could still apply to most runners or cyclists with knee pain even if not technically PFPS. In fact, seeing a healthcare professional would be more critical to rule out a more serious injury than necessarily diagnosis you with PFPS versus another similar overuse injury.
As discussed above the common variables contributing to PFPS include:
- Poor alignment with knee moving inward and/or patella being pulled outward
- Weak VMO and hip rotators and abductors
- Decreased flexibility in hip flexors, quadriceps, TFL, and hamstrings
- Poor running mechanics with knee moving inwards upon landing
- Training errors such as increasing mileage and/or speed too quickly or not getting proper recovery, sleep or nutrition
Most endurance athletes have some combination of most or all these issues going on whether or not they have PFPS, so many of the treatments could be preventative measures if currently injury free. Knowing which of these factors are most prevalent for you and thus in most need of correcting can be done using a clinician like a physical therapist, but addressing each can start to help you discover which may be your weak points.
Treatments for PFPS can include:
- Knee joint mobilizations
- Taping of the patella
- Use of orthotics
- Soft tissue techniques including foam rolling
- Strengthening weak muscles, specifically VMO and hip rotators and abductors
- Stretching of tight muscles, specifically hip flexors, quadriceps, TFL / IT Band, and hamstrings
- Re-training knee not to move inward upon landing by watching yourself in a mirror
- Working on landing “softer” i.e., quieter while running
- Correcting any training errors
While there is some evidence for all these treatments for effectiveness in treating PFPS, there is a lot of conflicting evidence and for several there is only evidence for using them in conjunction with other treatments, which can be common in this type of research. The takeaway here should be that the best approach is probably multi-pronged, using several or all of the above. Which ones you should focus more on are the ones that address your specific weaknesses. As said above a clinician can help identify some of these weaknesses but some self-experimentation can also give you a good idea. Other than the first 1 to 3 bullet points above, you should be able to implement most of the treatments above on your own. Examples of the stretches and strengthening exercises were included in this article. For a complete strength training plan which includes stretching routines see Endurance Strong’s strength training plans. As far as correcting training errors, one good approach would be following a proper training plan created by a quality coach, such as those created by Endurance Strong. Find Strength, Endurance, and Combination Training Plans here. Hopefully, this gives you a start in your road to recovery or some good information on how to prevent PFPS in the first place.
Note: Any of the above treatments or exercises you try, shouldn’t increase your pain levels especially in the knee joint other than typical discomfort in muscles one would feel with stretching, strengthening exercises, and soft tissue techniques. If you are unsure of this difference, then a clinician such as a physical therapist can help. None of the information in this article should take the place of medical advice and only be done with consent of a medical professional.
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