title: KOOS pain as a marker for significant knee pain two and six years after primary ACL reconstruction: a Multicenter Orthopaedic Outcomes Network (MOON) prospective longitudinal cohort study.
abstract: OBJECTIVE
  The prevalence of radiographic osteoarthritis (OA) after anterior cruciate ligament reconstruction (ACLR) approaches 50%, yet the prevalence of significant knee pain is unknown. We applied three different models of Knee injury and Osteoarthritis Outcome Score (KOOS) thresholds for significant knee pain to an ACLR cohort to identify prevalence and risk factors.
  
  
  METHODS
  Multicenter Orthopaedic Outcomes Network (MOON) prospective cohort patients with a unilateral primary ACLR and normal contralateral knee were assessed at 2 and 6 years. Independent variables included patient demographics, validated Patient Reported Outcomes (PRO; Marx activity score, KOOS), and surgical characteristics. Models included: (1) KOOS criteria for a painful knee = quality of life subscale <87.5 and ≥2 of: KOOSpain <86.1, KOOSsymptoms <85.7, KOOSADL <86.8, or KOOSsports/rec <85.0; (2) KOOSpain subscale score ≤72 (≥2 standard deviations below population mean); (3) 10-point KOOSpain drop from 2 to 6 years. Proportional odds models (alpha ≤ 0.05) were used.
  
  
  RESULTS
  1761 patients of median age 23 years, median body mass index (BMI) 24.8 kg/m(2) and 56% male met inclusion, with 87% (1530/1761) and 86% (1506/1761) follow-up at 2 and 6 years, respectively. At 6 years, n = 592 (39%), n = 131 (9%) and n = 169 (12%) met criteria for models #1 through #3, respectively. The most consistent and strongest independent risk factor at both time-points was subsequent ipsilateral knee surgery. Low 2-year Marx activity score increased the odds of a painful knee at 6 years.
  
  
  CONCLUSIONS
  Significant knee pain is prevalent after ACLR; with those who undergo subsequent ipsilateral surgery at greatest risk. The relationship between pain and structural OA warrants further study.
authors.affiliation: University of Toronto Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, MG301, Toronto, Ontario M4N 3M5, Canada. Electronic address: david.wasserstein@sunnybrook.ca.
authors.forename: D
authors.initials: D
authors.lastname: Wasserstein
authors.affiliation: Vanderbilt Sports Medicine, Vanderbilt University Medical Center, Nashville, TN, USA. Electronic address: laura.huston@vanderbilt.edu.
authors.forename: L J
authors.initials: LJ
authors.lastname: Huston
authors.affiliation: Department of Biostatistics, Vanderbilt University Medical Center, Nashville, TN, USA. Electronic address: sam.nwosu@vanderbilt.edu.
authors.forename: S
authors.initials: S
authors.lastname: Nwosu
authors.affiliation: Cleveland Clinic Sports Health, Cleveland Clinic, Cleveland, OH, USA. Electronic address: spindlk@ccf.org.
authors.forename: C C
authors.initials: CC
authors.lastname: Kaeding
authors.forename: R D
authors.initials: RD
authors.lastname: Parker
authors.forename: R W
authors.initials: RW
authors.lastname: Wright
authors.forename: J T
authors.initials: JT
authors.lastname: Andrish
authors.forename: R G
authors.initials: RG
authors.lastname: Marx
authors.forename: A
authors.initials: A
authors.lastname: Amendola
authors.forename: B R
authors.initials: BR
authors.lastname: Wolf
authors.forename: E C
authors.initials: EC
authors.lastname: McCarty
authors.forename: M
authors.initials: M
authors.lastname: Wolcott
authors.forename: W R
authors.initials: WR
authors.lastname: Dunn
authors.forename: K P
authors.initials: KP
authors.lastname: Spindler
mesh_terms: D000293:Adolescent; D000328:Adult; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction; D018771:Arthralgia / Q000453:epidemiology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007718:Knee Injuries / Q000601:surgery*; D008137:Longitudinal Studies; D008297:Male; D020370:Osteoarthritis, Knee / Q000453:epidemiology*; D015995:Prevalence; D011446:Prospective Studies; D011788:Quality of Life; D011795:Surveys and Questionnaires; D016896:Treatment Outcome; D055815:Young Adult
keywords: Anterior cruciate ligament reconstruction; Knee Injury and Osteoarthritis Outcome Score (KOOS); Knee pain; Symptomatic osteoarthritis