Knee pain is one symptom that we see a great deal of. Regardless of people’s age and activity level, the knees seem to be a vulnerable site of injury. In this particular post, I will be discussing one of the most common knee injuries; patellofemoral pain syndrome (PFPS).
PFPS is an overuse injury that is characterized by pain in the front aspect of the knee, typically along the medial or lateral aspect of the patella.[i] This condition is prevalent in many athletic populations, but is especially common in runners. The symptom presentation can vary, but most individuals will feel pain only with increased weight bearing activities (ex. Running, squatting).
There are several proposed mechanisms as to how this injury occurs.
1. Mechanical overload. This is when the repetitive stress of weight bearing activities overloads the ability of the knee to handle that given stress. For example, running can create forces on the knee up to 4.5 times one’s bodyweight.[ii] If the knee has not had adequate time to adapt to those forces, the knee is at risk of injury.
2. Lower limb muscle strength imbalances. Numerous studies have looked at this, however the results are quite mixed and thus may not be a cause for the onset of PFPS.
3. Lower limb running kinematics. Women with PFPS showed an increased hip adduction (HADD) and hip internal rotation (HIR) when they were in stance phase. Men with this condition had an increased
pelvic hip drop on the opposite side of the stance leg, and HADD.
4. There has also been evidence of delayed and shorter gluteus medius (GMed) activation during the stance phase in female runners classified as rearfoot strikers. [iii]
It is important to note the role of proper assessment techniques when it comes to PFPS. One such assessment is manual muscle testing. The assessor typically performs gluteal muscle tests in a side-lying position with manual resistance. However, according to Esculier et al 2015, reduced lower limb muscle strength testing may not correlate to knee pain syndromes in runners. Because of the fact that running is a dynamic activity, it is proposed that the main contributor to PFPS is lower limb control deficits as opposed to muscle strength.
Next post, I will discuss some treatment options to address this common ailment and what you can so to reduce your risk of injury.
Dr. Mike Rumeo is chiropractor with a passion for improving the health of his community and pain management. He primarily utilizes chiropractic, medical acupuncture and rehabilitation to help his patients. He is the owner of the Oakville Optihealth Clinic, a multidisciplinary clinic located at Fourth Line and South Service Rd W, in Oavkville ON. To contact Dr. Rumeo, please email him at firstname.lastname@example.org or call at 905.465.0202.
[i] Esculier, J.-F., Roy, J.-S., & Bouyer, L. J. (2015). Lower limb control and strength in runners with and without patellofemoral pain syndrome. Gait & Posture, 1–7. Elsevier B.V. doi:10.1016/j.gaitpost.2015.02.020
[ii] Esculier, J.-F., Roy, J.-S., & Bouyer, L. J. (2015). Lower limb control and strength in runners with and without patellofemoral pain syndrome. Gait & Posture, 1–7. Elsevier B.V. doi:10.1016/j.gaitpost.2015.02.020
[iii] Willson JD, Kernozek TW, Arndt RL, Reznichek DA, Scott Straker J. Gluteal muscle activation during running in females with and without patellofemoral pain syndrome. Clin Biomech 2011;26(7):735–40.