Article By : Auptimo (Systems for Gait & motion analysis)
UNDERSTANDING PATELLOFEMORAL PAIN IN RUNNERS
To manage patellofemoral pain in runners its important to understand the correlation between running biomechanics and its effect on the patellofemoral joint.
Patellofemoral pain syndrome (PFPS), most commonly known as ‘Runner’s knee‘ or anterior knee pain syndrome, is defined as “pain occurring around or behind the patella that is aggravated by at least one activity that loads the patella during weight-bearing on a flexed knee.”
- With an incidence of approximately 22 per 1000 persons, patellofemoral pain accounts for about 48.8% of knee injuries in runners.
- The incidence of PFPS in is higher in women (62%) as compared to men (38%) (Petersen W et al, 2013).
This is due to altered dynamic knee valgus, in which the knee collapses medially from excessive valgus, internal rotation of tibia, or rearfoot eversion.
This increases the lateral force on the patella, contributing to patellar maltracking (Myer GD, et al 2010)
The exact etiology of pain in PFPS is still unclear.
Hypothetically, the pain is generated at the insertions of the extensor muscles, retinacula, Hoffa’s fat pad and subchondral bone trauma (Gulati et al., 2018).
Overloading of the patellofemoral joint during high-intensity training activities may also be a possible trigger for PFPS.
The combination of overload with dynamic valgus & functional lateralization of the patella may lead to overuse of the structures of the patellofemoral joint and thus cause anterior knee pain (Petersen et al., 2014).
CLINICAL PRESENTATION (Gulati et al., 2018)
- Typically, an active young adult will present with gradual onset of anterior knee pain associated with a grinding sensation perceived on movement.
- The pain is often bilateral, usually more on one side, and is typically worsened by climbing or squatting activity, described by the patient “giving away or slipping”, which is due to quadriceps inhibition.
- It is difficult to localize and the patient may just place their hand on the knee or circumscribe the patella, referred to as the circle sign.
- A locking or catching sensation after prolonged flexion of the knee (rising from a seated posture) is observed, referred to as the “movie theatre sign”
POTENTIAL CAUSES OF PATELLOFEMORAL PAIN IN RUNNERS
Like any running injury, PFPS can be caused due to any musculoskeletal impairment, training errors, biomechanical faults & extrinsic factors like footwear etc.
In this section, we will be discussing assessments we can conduct to investigate each of these 4 aspects.
As a clinician, if we are able to figure out the root cause behind the injury, we can provide effective rehab for shin splints.
PART 1 : TRAINING ERRORS
Running is known to produce a great amount of loading in lower limb joints.
Hence, training errors are considered to contribute around 60% of running-related injuries.
Overtraining is one of the most common ‘Training Error’. It is often characterized by runners doing “too much”, “too soon”, “too often”, “too fast”, or “with too little rest”.
A mileage greater than 40 miles/week (64km/week) has been linked with an increased risk of running-related injuries, including patellofemoral pain (Nielsen et al., 2013).
In addition to the mileage, the rate of increase in weekly mileage should not exceed 10% of the current mileage. Secondly, an increase in the running pace should also be restricted to less than 3% per week.
For a complete set of running specific training guidelines, refer to this ‘UW Health Sports medicine runners book’.
When it comes to running surfaces, there’s a popular belief that running on softer surfaces is easier on the joints.
On the contrary, recent studies suggest that the overall stiffness of the body remains the same, irrespective of the surface. (Louie, et al., 1998)
In other words, the leg becomes stiffer while running on a softer surface, and more compliant while running on a harder surface.
This implies that the overall impact on the leg remains virtually the same whether running on grass, concrete or asphalt.
However, this finding should be treated with caution. According to Dr. Brian Heiderscheit, Director of the University of Wisconsin’s Runners’ Clinic, “We know how the body adjusts to different surfaces in the short term, but what we don’t know are the long term consequences of running on a particular surface” (MCMAHAN, 2020)
Hence, incorporating multiple running surfaces in training can be a good strategy to minimize the risk of injury.
As per Dr. Heiderscheit, “Just like a runner would try runs of different intensities—tempo and interval training for instance—my advice is to incorporate a little bit of all the different surfaces into training,” (MCMAHAN, 2020)
Downhill running tends to increase the Tibial loading and impact force at the knee. (Vernillo, et al., 2016) Hence, downhill training should not be recommended to runners with Patellofemoral Pain.
Training errors can be understood by taking a detailed injury & training history of the runner. Here’s a sample ‘Runner intake form‘ you can use to understand the patient better.
PART 2 : EXTRINSIC FACTORS (FOOTWEAR)
Footwear can hugely affect posture & biomechanics. An ‘incorrect’ pair of shoes can lead to several injuries, even if there is no physical limitation in the body.
A Clinical Assessment of the runner’s feet & shoe helps assess if the footwear needs to be replaced or while prescribing a new shoe.
Here’s a comprehensive guide you can refer to for a shoe assessment of runners.
PART 3 : BIOMECHANICS LINKED WITH PATELLOFEMORAL PAIN IN RUNNERS
A small degree of knee flexion is required at the moment of foot strike (initial contact) to ensure good shock absorption.
Now, imagine a case of an amateur runner looking to increase his running performance through an increase in stride length.
Such amateur runners tend to achieve this goal through increased knee extension at foot strike.
Although the strategy of knee extension is helpful from immediate performance point of view as it is increases the stride length.
However, this increases the ground reaction forces at the patellofemoral joint, leading to Runner’s knee problems.
CORRECTIONS: Typical overstriders hugely benefit from cadence retraining, a method that promotes shorter and faster steps instead of longer steps.
This ensures the same performance and better shock absorption at the knee joint.
Additionally, Refer to this link by Stanford Health for some drills.
Excessive Knee Flexion At Mid Stance
Knee flexion angle is highly predictive of peak patellofemoral joint force, such that peak force increases as knee flexion angle increases (Wille CM et al 2014).
Running with excessive knee flexion at Mid Stance (a moment when both knees are adjacent to each other) increases the patellofemoral joint stress & may require intervention.
Alternatively, some data exists suggesting that lower knee flexion (<40 degrees) may be associated with certain subgroups of patients with patellofemoral pain due to increased ground reaction forces (Dierks TA et al 2011).
So ideally, this angle should revolve around 40 degrees at mid stance.
CORRECTIONS: Along with a rehab program, Runners with excessive knee flexion at mid stance benefit from cadence retraining, a method that promotes shorter and faster steps instead of longer steps.
Moreover, Verbal cues to promote a softer landing are also helpful.
Excessive Contralateral Pelvic Drop
The event of mid stance (both knees are adjacent to each other) is accompanied by a small contralateral pelvic drop, generally greater in women as compared to men.
An excessive contralateral pelvic drop, increased hip adduction & internal rotation increases lateral stress on the patellofemoral joint, resulting in maltracking of the patella. (Dierks TA et al 2008)
CORRECTIONS: In addition to a rehab program, visual feedback to ask the runner to maintain a level pelvis is very helpful to prevent excessive contralateral pelvic drop.
Subtalar Over Pronation
Excessive pronation of subtalar joint in the midstance phase of the gait cycle can be a contributing factor to anterior knee pain associated with PFPS.
In addition to a rehab program, studies also recommend the use of orthotics (Kannus VP,1992) or higher level of support shoes to correct subtalar overpronation.
A running analysis is the most useful tool to detect biomechanical faults like overstriding or pelvic drop in a runner. Any running gait analysis software like GaitON can be used to do a comprehensive running analysis of the runner. All you need is the software and the slow motion video feature of your mobile phone to start.
PART 4 : MUSCULOSKELETAL IMPAIRMENTS
A physical examination of the knee should be performed in all patients with a chief symptom of anterior knee pain.
This helps in understanding if the injury is due to a physical limitation in the body or due to any other factor mentioned above.
The table below includes some commonly performed physical examination tests and their value in diagnosing PFPS. (Gaitonde, Ericksen and Robbins, 2019)
- Postural deviations like exaggerated lumbar lordosis, asymmetric hip height, foot overpronation, knee valgus, or atrophic (decreased muscle mass) quadriceps are generally visible in runners with PFPS.
- Hamstring (knee flexor) extensibility should also be checked as tight hamstrings have been associated with patellofemoral pain, possibly because of co-contraction of the hamstrings and quadriceps causing increased forces on the joint during exercise.
MANAGEMENT OF PATELLOFEMORAL PAIN IN RUNNERS
Clinical recommendations suggest most effectiveness with exercise therapy interventions followed by pain relieving medications.
Since multiple factors can contribute to PFPS, an individualized exercise therapy program is effective for managing patellofemoral pain in runners.
- Active rest is the principle mode of physical therapy in the acute phase of the condition. Any exacerbating movements or activities loading the knee joint should be avoided in the initial 2-3 weeks. Exercise regimens should focus on the hip, trunk, and knee.
- Secondly, some recommend active stretching exercises, squats, ergometer, static quadriceps exercises, active leg raises, leg press, raising and lowering climbing exercises.
- Thirdly, exercises to strengthen the hip abductors and trunk-stabilizing exercises, including the rectus abdominis, are also seen to benefit the patient. Exercises should be continued for 5-6 weeks. (Petersen W et al 2014)
3. Lastly, early therapies for PFPS include taping and foot orthotics can temporarily help improve patellar maltracking in athletes. Mc Connel taping is the most popular type of taping used in PFPS. The tape applies a medially directed force to counteract lateral patella maltracking (including tilt, rotation and shift).
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ABOUT THE AUTHOR
DR TEENA ELSA JOSEPH
Dr. Teena is a Sports Physiotherapist who has completed her BPT from Amity University & her MPT (Sports) from Indraprastha University. Her field of clinical expertise in sports & musculoskeletal physiotherapy includes manual therapy, dry needling & myofascial release. Apart from her work at Auptimo, she is also active as clinical researcher in a various of health & sports science research work at India Spinal Injuries Center, Delhi. She has achieved several awards for academic excellence along with professional certifications such as Dry Needling (Basic & Advanced), AHA certified BLS provider, NAEMT certified PHTLS provider, IRCS certified Senior professional in first aid, & NIDA certified Good Clinical Practitioner.
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