Development of a Clinical Hypothesis for Patellofemoral Pain ~ Irene Davis, PhD, PT

Patellofemoral pain (PFP) is a common orthopedic condition and the number one injury in runners.  Though the exact cause of PFP is unknown, it is believed to be related to the interaction between patella and femur. As the patella has seven articular facets, subtle abnormalities in the movement between the patella and femur can create areas of high patellofemoral joint contact stress and cause PFP.  Abnormal movements can also lead to abnormal loads on the soft tissues that stabilize the patella, causing PFP.

Photo by diongillard. Used with permission. All rights reserved. Source: flickr

Photo by diongillard. Used with permission. All rights reserved. Source: flickr

Due to the closed chain nature of lower extremity motion during gait, movement at one joint can affect others in the kinetic chain.  Mechanics of the hip, the knee, and the foot –or some combination of these factors- can affect patellofemoral motion. Debate continues as to which of these factors are the most prevalent and most important.  Understanding which factors are related to PFP is critical to developing the optimal rehabilitative approach. All treatment approaches should be based upon a clinical hypothesis.

A clinical hypothesis is your theory as to the cause of a patient’s problem, developed from their history, physical exam, and gait assessment.  The history provides information as to whether the injury is acute perhaps from improper training, or a chronic problem, which may be related to mechanics.  The physical exam provides insights into contributing factors in strength, flexibility, and alignment.  The gait assessment reveals faulty hip, knee, or foot mechanics that may overload key musculoskeletal structures.

Different presentations of these factors lead to different hypotheses.  In one case, you may hypothesize that the patient’s abnormal hip mechanics and weak hip musculature is resulting in genu valgus and patellofemoral malalignment.  In another patient, you may theorize that their excessively pronated and weak feet are leading to genu valgus, patellofemoral malalignment, and PFP.  In a third case, you may believe it is the patient’s long stride and heavy heel strike that is increasing the loads and rate of loading to the patellofemoral joint.

Based upon these three clinical hypotheses, your interventions will be very different.  The first patient might receive hip strengthening and gait retraining to improve their hip mechanics.  The second patient would focus on foot strengthening and gait retraining to better their foot mechanics.  Finally, the third patient might reduce their stride length and land softer.

As with research hypotheses, clinical hypotheses are not always correct and are tested by the success of the intervention.  If you find that your approach is not working you must reassess and refine or alter your clinical hypothesis. This type of approach provides a well-justified framework for your intervention. However, this requires an understanding of the potential factors that can contribute to PFP.

Understanding which factors are related to PFP is a large focus of the upcoming International Patellofemoral Pain Research Retreat.  Renowned scientists from across the globe will convene to discuss their most research in the area of PFP.  The Clinical Symposium Day will bring this research to the clinical arena. Along with keynote presentations on current topics, and debates on rehabilitation approaches, an expert panel will discuss difficult PFP cases. The consensus statement from the last International Patellofemoral Pain Research Retreat will be reviewed. Seldom do you have an opportunity to hear from this many scientific leaders in the area of PFP at one meeting -in one day.  Don’t miss it – Hope to see you there!

Dr. Irene Davis is the Director of the Spaulding National Running Center, Harvard Medical School. Dr. Davis’ research has focused on the relationship between lower extremity structure, mechanics and injury. Her interest in injury mechanics extends to the development of interventions to alter these mechanics through gait retraining.She has been featured on ABC World News Tonight, Good Morning America, Discovery, the New York Times, the Wall Street Journal, Parade, and Time Magazine.

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