title: Comparison of gluteus medius muscle activity during functional tasks in individuals with and without osteoarthritis of the hip joint.
abstract: BACKGROUND
  Neuromuscular alterations have been reported for patients with osteoarthritis of the hip joint; however, the underlying cause associated with altered gluteus medius muscle function has not been examined. This study assessed electromyographic amplitudes of the gluteus medius muscles during function in patients with unilateral end-stage osteoarthritis of the hip joint compared to controls.
  
  
  METHODS
  Patients with unilateral end-stage hip joint osteoarthritis (n=13) and asymptomatic control participants (n=17) participated. Average root-mean squared muscle amplitudes represented as a percent of maximum voluntary isometric contraction for both the involved and uninvolved limb gluteus medius muscles were analyzed during step up, step down, and gait. The association between muscle activation and impact forces during stepping tasks was assessed.
  
  
  RESULTS
  Patients with hip osteoarthritis exhibited increased gluteus medius muscle electromyographic amplitudes bilaterally during stair ascent, stair descent, and gait compared to controls, regardless of which limb they led. Involved limb muscle activity was inversely related to impact force during step down onto the ipsilateral limb.
  
  
  CONCLUSIONS
  Patients with hip osteoarthritis demonstrated increased gluteus medius muscle activation levels during stepping tasks and gait when compared to controls. The increased activation is most likely a compensatory response to muscle weakness. Therefore, application of strengthening exercises which target the gluteal muscles should assist in neuromuscular control and result in improved strength for patients with hip joint osteoarthritis.
authors.affiliation: Department of Rehabilitation Sciences, University of Kentucky, Lexington, KY, USA. Electronic address: mkdwyer@partners.org.
authors.forename: Maureen K
authors.initials: MK
authors.lastname: Dwyer
authors.forename: Kelly
authors.initials: K
authors.lastname: Stafford
authors.forename: Carl G
authors.initials: CG
authors.lastname: Mattacola
authors.forename: Timothy L
authors.initials: TL
authors.lastname: Uhl
authors.forename: Mauro
authors.initials: M
authors.lastname: Giordani
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D004576:Electromyography; D005081:Exercise Therapy; D005260:Female; D005684:Gait / Q000502:physiology; D006615:Hip / Q000502:physiology / Q000503:physiopathology*; D006621:Hip Joint / Q000502:physiology / Q000503:physiopathology; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D008875:Middle Aged; D018908:Muscle Weakness / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology; D018482:Muscle, Skeletal / Q000502:physiology / Q000503:physiopathology*; D015207:Osteoarthritis, Hip / Q000150:complications / Q000503:physiopathology*; D012016:Reference Values; D055815:Young Adult
keywords: Electromyography; Gait; Hip; Muscle; Osteoarthritis; Step test