title: The Knee injury and Osteoarthritis Outcome Score reflects the severity of knee osteoarthritis better than the revised Knee Society Score in a general Japanese population.
abstract: OBJECTIVE
  The purposes of this study were to examine population-based reference data for sex- and age-related differences between the 2011 revised Knee Society Score (KSS2011) and the Knee injury and Osteoarthritis Outcome Score (KOOS), to assess the correlation between those scores and radiographic knee osteoarthritis (OA), and to validate the use of the scores in a general Japanese population.
  
  
  METHODS
  This cross-sectional study included 963 volunteers (368 males, 595 females; mean age: 54.7years). Participants were classified into five subgroups by age: under 40, 40s, 50s, 60s, and over 70years old. The KSS2011 and KOOS were determined using self-administered questionnaires. Weight-bearing radiographs of the bilateral knee were taken and graded according to the Kellgren-Lawrence (KL) scale. The mean KSS2011 and KOOS were compared among age groups. Correlations between the severity of knee OA and each score were assessed using multiple regression analysis.
  
  
  RESULTS
  The overall KSS2011 tended to gradually decrease with age. Most subscales of the KSS2011 did not show sex-related differences. Similarly, the overall KOOS and all its subscales steadily decreased by approximately 20 points per decade with age. Most subscales of the KOOS were significantly decreased in females over 50. The KL grade was significantly related to both the overall KOOS (β=-0.42, p<0.001) and KSS2011 (β=-0.13, p=0.001), though the correlation to the KOOS was stronger.
  
  
  CONCLUSIONS
  The overall KSS2011 and KOOS appear to decrease with age. In this population, the KOOS reflects the severity of knee OA better than the KSS2011.
authors.affiliation: Department of Orthopedic Surgery, Hirosaki University Graduate School of Medicine, Hirosaki, Japan.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Oishi
authors.affiliation: Department of Orthopedic Surgery, Hirosaki University Graduate School of Medicine, Hirosaki, Japan.
authors.forename: Eiichi
authors.initials: E
authors.lastname: Tsuda
authors.affiliation: Department of Orthopedic Surgery, Hirosaki University Graduate School of Medicine, Hirosaki, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Yamamoto
authors.affiliation: Department of Orthopedic Surgery, Hirosaki University Graduate School of Medicine, Hirosaki, Japan.
authors.forename: Shugo
authors.initials: S
authors.lastname: Maeda
authors.affiliation: Department of Orthopedic Surgery, Hirosaki University Graduate School of Medicine, Hirosaki, Japan.
authors.forename: Eiji
authors.initials: E
authors.lastname: Sasaki
authors.affiliation: Department of Orthopedic Surgery, Hirosaki University Graduate School of Medicine, Hirosaki, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Chiba
authors.affiliation: Department of Social Medicine, Hirosaki University Graduate School of Medicine, Hirosaki, Japan.
authors.forename: Ippei
authors.initials: I
authors.lastname: Takahashi
authors.affiliation: Department of Social Medicine, Hirosaki University Graduate School of Medicine, Hirosaki, Japan.
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Nakaji
authors.affiliation: Department of Orthopedic Surgery, Hirosaki University Graduate School of Medicine, Hirosaki, Japan.
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Ishibashi
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D007718:Knee Injuries / Q000150:complications / Q000175:diagnosis* / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000175:diagnosis* / Q000453:epidemiology / Q000209:etiology; D017063:Outcome Assessment, Health Care / Q000379:methods*; D011379:Prognosis; D011788:Quality of Life; D012189:Retrospective Studies; D012720:Severity of Illness Index; D012955:Societies, Medical; D011795:Surveys and Questionnaires; D055815:Young Adult
keywords: General population; Knee Society Score; Knee injury and Osteoarthritis Outcome Score; Knee osteoarthritis