title: Knee Injury and Osteoarthritis Outcome Score has higher responsiveness and lower ceiling effect than Knee Society Function Score after total knee arthroplasty.
abstract: OBJECTIVE
  To compare the following subjective scoring instruments: the Knee Society Function (KS-F) Score and Knee Injury and Osteoarthritis Outcome Score (KOOS) in patients who underwent total knee arthroplasty (TKA) by assessing standard metrics related to the utility of each instrument, including responsiveness, ceiling effect, and distribution of scores.
  
  
  METHODS
  Patients undergoing TKA for osteoarthritis (n = 82) were evaluated pre-operatively and post-operatively at a median time of 1 year (range 0.7-3.6 years) using the KS-F score and KOOS. Responsiveness, the ability of a tool to measure change over time, was evaluated by computing the standardized response mean. Ceiling effects were determined by calculating the percentage of patients who attained the best-possible score.
  
  
  RESULTS
  The KOOS scale had higher standardized response mean than KS-F scale in the majority of subsections (except sports and recreation). The KOOS had a lower ceiling effect in the majority of subsections (except pain) and was significantly lower on the symptoms and quality of life subscales (both p < 0.05). Scores were not normally distributed for either KS-F or KOOS scales.
  
  
  CONCLUSIONS
  Since the KOOS scale had a higher responsiveness and a lower ceiling effect, it appears to be a superior outcome tool versus the KS-F scale when evaluating the outcomes of TKA patients.
  
  
  METHODS
  Diagnostic Study, Level I.
authors.affiliation: Kaiser Permanente Orthopedics, San Marcos Outpatient Medical Center, 400 Craven Rd, San Marcos, CA, 92078, USA.
authors.forename: Amy K
authors.initials: AK
authors.lastname: Steinhoff
authors.affiliation: Division of Orthopaedic Surgery, Scripps Clinic, 10666 North Torrey Pines Road, MS 116, La Jolla, CA, 92037, USA. Bugbee.William@scrippshealth.org.
authors.forename: William D
authors.initials: WD
authors.lastname: Bugbee
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee; D005260:Female; D019538:Health Care Surveys; D006801:Humans; D007718:Knee Injuries / Q000601:surgery*; D007719:Knee Joint / Q000601:surgery; D008297:Male; D020370:Osteoarthritis, Knee / Q000601:surgery*; D011184:Postoperative Period; D011788:Quality of Life; D016896:Treatment Outcome
keywords: Ceiling effect; Knee Injury and Osteoarthritis Outcome Score; Knee Society Function Score; Standardized response mean; Total knee arthroplasty