Fans of Dr. Janda’s work know it’s always important to evaluate more than just the area of pain, particularly the proximal segments of a more distal pathology. Recently, hip weakness was associated with anterior knee pain in several studies, as suggested by Janda. These proximal muscle imbalances are thought to lead to altered motor control strategies and subsequent abnormal biomechanics at the knee during the stance phase of gait.
A new study from the United Kingdom on football (soccer) players with chronic groin strains found decreased gluteus medius (hip abductor) muscle activation on the injured leg. Healthy and injured subjects performed standing hip flexion to 90 degrees while Noraxon® surface electromyography (EMG) was collected. The activation ratio was determined between the hip abductors and adductors of the injured leg during both flexion and stance. The researchers also analyzed time-to-onset of muscle activation. Interestingly, this imbalance occurred in both the stance phase and kicking phase of a standing hip flexion test in the injured athletes. This decrease in activation led to muscle imbalance between the hip abductors and adductors. Tyler and colleagues (2001) also demonstrated hip muscle imbalance in the kicking leg of soccer players with groin injuries, although they showed weakness of the hip adductor muscles.
The researchers found a 40 to 50% decrease in activation and subsequently significant reduction in hip abductor:hip adductor ratio in the injured leg during stance. Muscle activation was delayed during all phases of movement as well. Interestingly, the athletes with chronic groin pain demonstrated muscle imbalances on the uninjured side as well. This result surprised the researchers, but clinicians often see these global imbalances in chronic musculoskeletal pain, supporting the etiology resulting from CNS dysregulation.
REFERENCE: Morrissey D, et al. Coronal plane hip muscle activation in football code athletes with chronic adductor groin strain injury during standing hip flexion. Man Ther. 2012 Apr;17(2):145-9.
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