title: Quadriceps muscle strength and its relationship to radiographic knee osteoarthritis in Japanese elderly.
abstract: BACKGROUND
  Knee osteoarthritis (OA) is a multifactorial disease and strongly affected by mechanical factors. The aims of the present study were to assess validity and reliability of a new muscle strength measuring device, the Quadriceps Training Machine (QTM) and evaluate the relationship between quadriceps strength measured by QTM and radiographic knee OA by epidemiological survey.
  
  
  METHODS
  The isometric knee extension muscle strength of QTM was compared with BIODEX in 24 healthy adults. Then, the relationship between radiographic knee OA and quadriceps strength using QTM was investigated with 2,032 knees in 1,016 subjects by an epidemiological survey (Matsudai Knee Osteoarthritis Survey).
  
  
  RESULTS
  Significant correlation was observed between QTM and BIODEX (r = 0.69, 0.82). In the Matsudai Knee Osteoarthritis Survey, the prevalence of radiographic OA (grade II or higher upon Kellgren-Lawrence classification) was: 13, 36.9, 67.8, and 86.5 %, regarding women in their fifties, sixties, seventies, and eighties, respectively, and was 1.7, 13.4, 33.5, and 66.2 % regarding men, respectively. Quadriceps muscle strength declined following 50 years of age, and significant decline was observed in the their sixties and seventies. Quadriceps muscle strength of the OA group (grades II, III and IV) was significantly declined compared with that of the Non-OA group (grade-0 and I). Furthermore, the tendency of the muscle strength level to decline with the progression of knee OA grade was particularly observed between grade 0 and grade I in both men and women and between grade I and grade II in men.
  
  
  CONCLUSIONS
  The relationship between radiographic knee OA and quadriceps strength was quantitatively evaluated by an epidemiological survey, and we found a correlation between knee OA and the decline in quadriceps strength. Furthermore, it was suggested that the decline in quadriceps muscle strength may be more strongly related to the incidence of knee OA than to its progression.
authors.affiliation: Center of Transdisciplinary Research, Institute for Research Promotion, Niigata University, 2-8050, Igarashi, Nishi-ku, Niigata City 950-2181, Niigata, Japan. gosuke@med.niigata-u.ac.jp
authors.forename: Go
authors.initials: G
authors.lastname: Omori
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Koga
authors.forename: Masaei
authors.initials: M
authors.lastname: Tanaka
authors.forename: Atsushi
authors.initials: A
authors.lastname: Nawata
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Watanabe
authors.forename: Kentaro
authors.initials: K
authors.lastname: Narumi
authors.forename: Kazuo
authors.initials: K
authors.lastname: Endoh
mesh_terms: D000368:Aged; D044466:Asian People; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D052097:Quadriceps Muscle / Q000503:physiopathology*; D011859:Radiography