title: Knee extensor strength does not protect against incident knee symptoms at 30 months in the multicenter knee osteoarthritis (MOST) cohort.
abstract: OBJECTIVE
  Knee extensor weakness has not been associated consistently with the risk for incident knee pain. Additionally, the balance of hamstring-to-quadriceps strength (H:Q ratio) may affect risk and has not been studied. The authors determined whether knee extensor weakness or muscle imbalance is a risk factor for development of frequent knee pain or stiffness and whether the effect is modified by lower limb alignment.
  
  
  METHODS
  Observational study.
  
  
  METHODS
  Community.
  
  
  METHODS
  Community-dwelling adults ages 50-79 years with or at risk of knee osteoarthritis based on obesity, knee injury, or surgery. A total of 1269 knees from women and 1006 knees from men without frequent knee symptoms at baseline and with 15- or 30- month follow-up outcome data were included.
  
  
  METHODS
  Isokinetic knee extensor and flexor strength as well as radiographic hip-knee-ankle alignment were measured at baseline. H:Q ratio was dichotomized, with normal being considered to be >/=0.6.
  
  
  METHODS
  Frequent knee symptoms at 15- or 30-month follow-up (frequent knee pain, aching, or stiffness on most days of the past month reported at both telephone contact just before and at visit).
  
  
  RESULTS
  Mean +/- SD age was 62.2 +/- 8.0 years and mean body mass index (BMI) was 30.1 +/- 5.4 kg/m(2). Mean peak knee extensor strength (KES) was 132.6 +/- 42.4 and 76.9 +/- 25.3 N.m in men and women, respectively. Approximately 50% of knees in men and 59% of knees in women had an H:Q ratio <0.6. A total of 307 of 2275 eligible knees developed frequent knee symptoms at follow-up. Logistic regression controlling for age, BMI, femoral neck bone mineral density, activity score, and baseline Kellgren Lawrence grade revealed that neither KES nor H:Q ratio predicted the development of knee symptoms in gender-stratified or combined analyses. These results were unaffected by adjusting for lower limb alignment.
  
  
  CONCLUSIONS
  Neither concentric quadriceps strength nor H:Q ratios predicted the development of frequent knee symptoms at 15- or 30-month follow-up in this cohort.
authors.affiliation: Department of Orthopaedics and Rehabilitation, University of Iowa, 200 Hawkins Drive, 0728 JPP, Iowa City, IA 52242-1088, USA. segal-research@uiowa.edu
authors.forename: Neil A
authors.initials: NA
authors.lastname: Segal
authors.forename: James C
authors.initials: JC
authors.lastname: Torner
authors.forename: David T
authors.initials: DT
authors.lastname: Felson
authors.forename: Jingbo
authors.initials: J
authors.lastname: Niu
authors.forename: Leena
authors.initials: L
authors.lastname: Sharma
authors.forename: Cora E
authors.initials: CE
authors.lastname: Lewis
authors.forename: Michael
authors.initials: M
authors.lastname: Nevitt
mesh_terms: D000368:Aged; D018771:Arthralgia / Q000453:epidemiology*; D016022:Case-Control Studies; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D020370:Osteoarthritis, Knee / Q000150:complications* / Q000503:physiopathology*; D004856:Postural Balance / Q000502:physiology; D052097:Quadriceps Muscle / Q000503:physiopathology*; D016059:Range of Motion, Articular / Q000502:physiology*; D016474:Weight-Bearing / Q000502:physiology