title: Hip strength and knee pain in high school runners: a prospective study.
abstract: OBJECTIVE
  To determine whether pre-injury hip muscle weakness is associated with the development of patellofemoral pain (PFP) in high school running athletes.
  
  
  METHODS
  Prospective cohort study.
  
  
  METHODS
  Academic institution sports medicine center.
  
  
  METHODS
  High school running athletes.
  
  
  METHODS
  Baseline hip strength of high school running athletes was assessed at the beginning of the running season. Strength testing was repeated in athletes who developed PFP. Peak hip muscle strengths and strength ratios were compared between the injured and non-injured groups.
  
  
  RESULTS
  Six injuries occurred in 5 of the 98 subjects who completed the study. The baseline hip external-to-internal strength ratio was lower in injured than in uninjured subjects (P = .008). In the injured group, hip abduction and external rotation strengths decreased from pre-injury to post-injury (P = .002 and P = .01, respectively). Logistic regression analysis demonstrated that a greater baseline hip abduction strength (odds ratio = 5.35, 95% confidence interval [CI] 1.46-19.53; P < .01) and abduction-to-adduction strength ratio increased the risk of injury (odds ratio = 14.14, 95% CI 0.90-221.06; P = .05), and a greater pre-injury hip external-to-internal rotation strength ratio decreased the risk of injury (odds ratio < 0.01, 95% CI ≤ .01, 0.44; P = .02).
  
  
  CONCLUSIONS
  The findings of the current study suggest that stronger pre-injury hip abductors (particularly in relation to their hip adductors) and weaker pre-injury hip external rotators (particularly in relation to their hip internal rotators) are associated with the development of PFP. In addition, persons in whom PFP develops appear to lose hip abduction and external rotation strength when compared with their pre-injury strength. Finally, a higher hip external-to-internal rotation strength ratio may protect against the development of PFP.
authors.affiliation: Department of Physical Medicine and Rehabilitation, Mayo Clinic College of Medicine, Mayo Clinic Sports Medicine Center, 200 1st St SW, Rochester, MN 55905, USA. Finnoff.jonathan@mayo.edu
authors.forename: Jonathan T
authors.initials: JT
authors.lastname: Finnoff
authors.forename: Mederic M
authors.initials: MM
authors.lastname: Hall
authors.forename: Kelli
authors.initials: K
authors.lastname: Kyle
authors.forename: David A
authors.initials: DA
authors.lastname: Krause
authors.forename: Jim
authors.initials: J
authors.lastname: Lai
authors.forename: Jay
authors.initials: J
authors.lastname: Smith
mesh_terms: D000293:Adolescent; D005260:Female; D006621:Hip Joint / Q000502:physiology* / Q000503:physiopathology*; D006801:Humans; D058745:Iliotibial Band Syndrome / Q000503:physiopathology*; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D053580:Muscle Strength; D046788:Patellofemoral Pain Syndrome / Q000503:physiopathology*; D012420:Running / Q000293:injuries* / Q000502:physiology