title: Association of mechanical factors with medial knee osteoarthritis: A cross-sectional study from Matsudai Knee Osteoarthritis Survey.
abstract: BACKGROUND
  Knee osteoarthritis (OA) is a multifactorial disease that is affected by mechanical factors. The aim of present study was to investigate the association between multiple mechanical factors and medial knee OA in a large epidemiological cohort.
  
  
  METHODS
  Six hundred and ninety-nine subjects (323 males and 376 females), participating in the Matsudai Knee Osteoarthritis Survey 2010, were included. Twelve mechanical factors were selected and their association with the radiographic grade of knee OA, the Western Ontario and McMaster University Index (WOMAC) pain score, and the WOMAC function score was evaluated.
  
  
  RESULTS
  A logistic regression analysis identified varus thrust to be associated with the radiographic grade of knee OA in males (OR: 1.876, 95% CI: 1.332-2.663) and females (2.61, 1.922-3.542), the WOMAC pain score in males (1.997, 1.463-2.672), and the WOMAC function score in females (1.449, 1.12-1.874). Quadriceps muscle strength was associated with the radiographic OA grade in males (0.605, 0.399-0.917) and females (0.636, 0.469-0.863), the WOMAC pain score in females (0.537, 0.445-0.789), and the WOMAC function score in males (0.581, 0.44-0.766). The knee flexion angle was also associated with the radiographic OA grade in males (0.344, 0.19-0.621) and females (0.121, 0.022-0.653), and the WOMAC pain score in males (0.287, 0.156-0.53) and females (0.537, 0.336-0.859). Obesity was associated with the radiographic OA grade in males (1.543, 1.041-2.287) and females (1.589, 1.176-2.146), the WOMAC pain score in female (2.017, 1.517-2.68). Femolo-tibial angle had no significant association with the radiographic knee OA grade or with the WOMAC pain and function scores.
  
  
  CONCLUSIONS
  Among patients with medial knee OA, dynamic mechanical factors, such as varus thrust, quadriceps muscle strength, and range of motion were more likely to be associated with the radiographic grade of knee OA and to be the WOMAC pain and function scores, compared to static mechanical factors.
authors.affiliation: Department of Health and Sports, Faculty of Health and Science, Niigata University of Health and Welfare, Japan. Electronic address: omori@nuhw.ac.jp.
authors.forename: Go
authors.initials: G
authors.lastname: Omori
authors.affiliation: Medical Engineering Laboratory, Alcare Co., Ltd., Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Narumi
authors.affiliation: Niigata Institute for Health and Sports Medicine, Japan.
authors.forename: Katsutoshi
authors.initials: K
authors.lastname: Nishino
authors.affiliation: Medical Engineering Laboratory, Alcare Co., Ltd., Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Nawata
authors.affiliation: Department of Rehabilitation, Sanjo General Hospital, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Watanabe
authors.affiliation: Medical Engineering Laboratory, Alcare Co., Ltd., Japan.
authors.forename: Masaei
authors.initials: M
authors.lastname: Tanaka
authors.affiliation: Department of Health and Nutrition, Faculty of Health and Science, Niigata University of Health and Welfare, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Endoh
authors.affiliation: Orthopaedic Surgery, Ninoji Onsen Hospital, Japan.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Koga
mesh_terms: D000368:Aged; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength; D020370:Osteoarthritis, Knee / Q000150:complications* / Q000000981:diagnostic imaging / Q000503:physiopathology*; D010147:Pain Measurement; D016059:Range of Motion, Articular; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D016474:Weight-Bearing