title: Knee Injury and Osteoarthritis Outcome Score (KOOS): systematic review and meta-analysis of measurement properties.
abstract: To conduct a systematic review and meta-analysis to synthesize evidence regarding measurement properties of the Knee injury and Osteoarthritis Outcome Score (KOOS).
  
  
  
  A comprehensive literature search identified 37 eligible papers evaluating KOOS measurement properties in participants with knee injuries and/or osteoarthritis (OA). Methodological quality was evaluated using the COSMIN checklist. Where possible, meta-analysis of extracted data was conducted for all studies and stratified by age and knee condition; otherwise narrative synthesis was performed.
  
  
  
  KOOS has adequate internal consistency, test-retest reliability and construct validity in young and old adults with knee injuries and/or OA. The ADL subscale has better content validity for older patients and Sport/Rec for younger patients with knee injuries, while the Pain subscale is more relevant for painful knee conditions. The five-factor structure of the original KOOS is unclear. There is some evidence that the KOOS subscales demonstrate sufficient unidimensionality, but this requires confirmation. Although measurement error requires further evaluation, the minimal detectable change for KOOS subscales ranges from 14.3 to 19.6 for younger individuals, and ≥20 for older individuals. Evidence of responsiveness comes from larger effect sizes following surgical (especially total knee replacement) than non-surgical interventions.
  
  
  
  KOOS demonstrates adequate content validity, internal consistency, test-retest reliability, construct validity and responsiveness for age- and condition-relevant subscales. Structural validity, cross-cultural validity and measurement error require further evaluation, as well as construct validity of KOOS Physical function Short form. Suggested order of subscales for different knee conditions can be applied in hierarchical testing of endpoints in clinical trials.
  
  
  
  PROSPERO (CRD42011001603).
authors.affiliation: School of Health and Rehabilitation Sciences, The University of Queensland, St Lucia, Queensland, Australia; Department of Mechanical Engineering, Melbourne School of Engineering, The University of Melbourne, Parkville, Victoria, Australia. Electronic address: n.collins1@uq.edu.au.
authors.forename: N J
authors.initials: NJ
authors.lastname: Collins
authors.affiliation: VU University Medical Center, Department of Epidemiology and Biostatistics, EMGO Institute for Health and Care Research, The Netherlands. Electronic address: c.prinsen@vumc.nl.
authors.forename: C A C
authors.initials: CA
authors.lastname: Prinsen
authors.affiliation: Musculoskeletal Statistics Unit, The Parker Institute, Bispebjerg and Frederiksberg Hospital, Copenhagen, Denmark. Electronic address: robin.christensen@regionh.dk.
authors.forename: R
authors.initials: R
authors.lastname: Christensen
authors.affiliation: The Biochemistry and Physiology Laboratory, The Parker Institute, Bispebjerg and Frederiksberg Hospital, Copenhagen, Denmark. Electronic address: Else.Marie.Bartels@regionh.dk.
authors.forename: E M
authors.initials: EM
authors.lastname: Bartels
authors.affiliation: VU University Medical Center, Department of Epidemiology and Biostatistics, EMGO Institute for Health and Care Research, The Netherlands. Electronic address: cb.terwee@vumc.nl.
authors.forename: C B
authors.initials: CB
authors.lastname: Terwee
authors.affiliation: Research Unit for Musculoskeletal Function and Physiotherapy, Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark. Electronic address: eroos@health.sdu.dk.
authors.forename: E M
authors.initials: EM
authors.lastname: Roos
mesh_terms: D006801:Humans; D007718:Knee Injuries; D007719:Knee Joint; D020370:Osteoarthritis, Knee; D011594:Psychometrics; D015203:Reproducibility of Results
keywords: KOOS; Knee injury; Knee osteoarthritis; Measurement properties; Meta-analysis; Patient-reported outcome measures