Gluteal Muscle Activation during running in females with and without patellofemoral pain syndrome

Willson JD, Kernozek TW, Arndt RL, Reznichek DA, Scott Straker J. Clin Biomech (Bristol, Avon). 2011 Mar 7. [Epub ahead of print]

Running is one of the most common activities. If it’s not running as a sport itself, people are running to prepare for their sport or maybe even just to stay in shape. One of the common overuse injuries that occurs in runners is patellofemoral pain syndrome (PFPS). Many studies have investigated PFPS and have shown that females are two times more likely to develop it than men. In addition, decreased hip strength is one of the most consistent published finding associated with PFPS. The purpose of this study was to examine the magnitude and timing of gluteus medius (GMED) and gluteus maximus (GMAX) muscle activities among females with and without PFPS during running. The authors gathered a group of 20 females with PF pain and a group of 20 females without any knee pain. All participants were evaluated with 3D running kinematics, kinetics, and GMED and GMAX EMG (electromyography). They found that females with patellofemoral pain demonstrated a delayed and shorter GMED activation compared to the females without knee pain during the stance phase of running. They also found greater hip adduction and internal rotation joint excursion (range of motion) which was also correlated with later GMED and GMAX EMG activity in the PFPS group.

This study is important to support and identify several biomechanical and neuromuscular dysfunctions at the hip in patients experiencing PFPS. The main finding showed that patients with PFPS have a delayed muscle activation of the GMED. They also showed that these patients had greater amounts of hip adduction and internal rotation joint excursion than those without knee pain. These are interesting findings that have been theorized for several years. Although these findings establish associations between biomechanical and neuromuscular dysfunctions and PFPS, they cannot decipher whether these findings are the causes of PFPS or the result of the pain associated with PFPS. The EMG results correlating with the biomechanics suggest that the dysfunction of the GMED lead to positioning the femur in adduction and internal rotation. This position, over time, will lead to discomfort by causing the patella to track laterally during running. This laterally tracking patella outside the femoral groove will cause a repetitively large compression force to the patellar articular cartilage. By addressing these deficiencies in the hip, the femur can be properly repositioned during the stance phase to improve the efficiency of patellar tracking alleviating the repetitively large compression forces. This ultimately can lead to resolution of the individual’s pain. What are your thoughts on this concept of realigning the patella by correcting the position of the femur instead of realigning the patella with use of tape, bracing, or VMO exercises?

Written by: Tommy Nowakowski Jr.
Reviewed by: Stephen Thomas