title: A Meta-Analysis to Determine if Lower Extremity Muscle Strengthening Should Be Included in Military Knee Overuse Injury-Prevention Programs.
abstract: BACKGROUND
  Knee overuse injuries are the most common musculoskeletal complaints in military trainees and are common in active-duty warfighters. Muscle strengthening is usually recommended; however, research is conflicting in this area, which makes it difficult to develop effective screening, prevention, and training interventions for warfighters.
  
  
  OBJECTIVE
  To determine if lower extremity muscular weakness contributes to knee overuse injuries and identify specific muscular involvement.
  
  
  METHODS
  We searched MEDLINE, PubMed, Web of Science, SPORTDiscus, CINAHL, and Military & Government Collection and reference lists of relevant articles published between January 1, 2000, and January 1, 2013.
  
  
  METHODS
  For inclusion, requirements were uninjured and injured groups; provision of the sample size, means, and standard deviations for all groups; identification of the specific muscles assessed; and clearly defined knee injury.
  
  
  METHODS
  Sample size, sex, and muscle strength means and standard deviations.
  
  
  RESULTS
  Twenty-five studies met these criteria. We used the Scottish Intercollegiate Guidelines Network algorithm to determine the appropriate tool for appraising article quality. Unweighted random-effects model meta-analyses were conducted. Separate meta-analyses were performed for the moderators of strength measurement scale (absolute or normalized muscle strength), muscle group, and sex. A weighted random-effects model with a Hedges g effect metric and 95% confidence intervals were used for comparison across studies.
  
  
  CONCLUSIONS
  Our meta-analysis suggests that individuals with symptoms of a knee overuse injury have lower absolute and normalized hip muscle strength. Specifically, they had lower absolute hip external-rotator, knee-extensor, and knee-flexor strength, as well as lower normalized hip external-rotator, hip-extensor, and hip-abductor strength, compared with asymptomatic control participants. The findings suggest a possible link between lower hip and thigh strength and knee overuse injuries. Further research is needed to determine if weakness is a cause or a result of knee overuse injuries before screening and intervention can be developed for at-risk warfighters.
authors.affiliation: Department of Kinesiology and Rehabilitative Sciences, University of Tulsa, OK.
authors.forename: Roger O
authors.initials: RO
authors.lastname: Kollock
authors.affiliation: Athletic Training Post-Certification Graduate Program, Auburn University, AL.
authors.forename: Corey
authors.initials: C
authors.lastname: Andrews
authors.affiliation: Athletic Training Post-Certification Graduate Program, Auburn University, AL.
authors.forename: Ashlyn
authors.initials: A
authors.lastname: Johnston
authors.affiliation: Athletic Training Post-Certification Graduate Program, Auburn University, AL.
authors.forename: Teresa
authors.initials: T
authors.lastname: Elliott
authors.affiliation: School of Fisheries, Aquaculture, and Aquatic Sciences, Auburn University, AL.
authors.forename: Alan E
authors.initials: AE
authors.lastname: Wilson
authors.affiliation: Department of Applied Medicine and Rehabilitation, Indiana State University.
authors.forename: Kenneth E
authors.initials: KE
authors.lastname: Games
authors.affiliation: Warrior Research Center, School of Kinesiology, Auburn University, AL.
authors.forename: JoEllen M
authors.initials: JM
authors.lastname: Sefton
mesh_terms: D012090:Cumulative Trauma Disorders / Q000175:diagnosis / Q000503:physiopathology*; D006801:Humans; D007718:Knee Injuries / Q000175:diagnosis / Q000503:physiopathology / Q000517:prevention & control*; D008889:Military Personnel; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*
keywords: hip strength; iliotibial band syndrome; patellofemoral pain syndrome; warfighters