title: Does clinically important change in function after knee replacement guarantee good absolute function? The multicenter osteoarthritis study.
abstract: OBJECTIVE
  Poor functional outcomes post-knee replacement are common, but estimates of its prevalence vary, likely in part because of differences in methods used to assess function. The agreement between improvement in function and absolute good levels of function after knee replacement has not been evaluated. We evaluated the attainment of improvement in function and absolute good function after total knee replacement (TKR) and the agreement between these measures.
  
  
  METHODS
  Using data from The Multicenter Osteoarthritis (MOST) Study, we determined the prevalence of achieving a minimal clinically important improvement (MCII, ≥ 14.2/68 point improvement) and Patient Acceptable Symptom State (PASS, ≤ 22/68 post-TKR score) on the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Physical Function subscale at least 6 months after knee replacement. We also assessed the frequency of co-occurrence of the 2 outcomes, and the prevalence according to pre-knee replacement functional status.
  
  
  RESULTS
  We included 228 subjects who had a knee replacement during followup (mean age 65 yrs, mean body mass index 33.4, 73% female). Seventy-one percent attained the PASS for function after knee replacement, while only 44% attained the MCII. Of the subjects who met the MCII, 93% also attained the PASS; however, of subjects who did not meet the MCII, 54% still achieved a PASS. Baseline functional status was associated with attainment of each MCII and PASS.
  
  
  CONCLUSIONS
  There was only partial overlap between attainment of a good level of function and actually improving by an acceptable amount. Subjects were more likely to attain an acceptable level of function than to achieve a clinically important amount of improvement post-knee replacement.
authors.affiliation: From the Department of Physical Therapy and Athletic Training, College of Health and Rehabilitation Sciences, Boston University; Clinical Epidemiology Training Unit, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts, USA.
authors.forename: Jessica L
authors.initials: JL
authors.lastname: Maxwell
authors.forename: David T
authors.initials: DT
authors.lastname: Felson
authors.forename: Jingbo
authors.initials: J
authors.lastname: Niu
authors.forename: Barton
authors.initials: B
authors.lastname: Wise
authors.forename: Michael C
authors.initials: MC
authors.lastname: Nevitt
authors.forename: Jasvinder A
authors.initials: JA
authors.lastname: Singh
authors.forename: Laura
authors.initials: L
authors.lastname: Frey-Law
authors.forename: Tuhina
authors.initials: T
authors.lastname: Neogi
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000503:physiopathology / Q000601:surgery*; D010147:Pain Measurement; D017060:Patient Satisfaction; D020127:Recovery of Function / Q000502:physiology*; D012720:Severity of Illness Index; D016896:Treatment Outcome
keywords: KNEE REPLACEMENT; OUTCOMES; PHYSICAL FUNCTION