title: Six-year course and prognosis of nontraumatic knee symptoms in adults in general practice: a prospective cohort study.
abstract: OBJECTIVE
  To examine the 6-year course of nontraumatic knee symptoms in adults in general practice, to identify prognostic factors for unfavorable outcome, and to develop a clinical prediction rule.
  
  
  METHODS
  Adults (ages >35 years) with incident nontraumatic knee symptoms (n = 549) were followed for 6 years. Multivariable logistic regression analysis was used to identify prognostic factors associated with an unfavorable outcome, the area under the receiver operating curve (AUC) was calculated to determine discriminative ability, and a clinical prediction rule was developed. Unfavorable outcome is defined as persistent knee symptoms at 6-year followup or having undergone knee replacement surgery during followup.
  
  
  RESULTS
  At 6-year followup, 42.1% of patients had an unfavorable outcome. Having persistent knee symptoms (odds ratio [OR] 5.31, 95% confidence interval [95% CI] 3.27-8.61) and fulfilling the clinical American College of Rheumatology (ACR) criteria for osteoarthritis (OA; OR 2.65, 95% CI 1.48-4.73) at 1-year followup were significantly associated with unfavorable outcome, while fulfilling the clinical ACR criteria for OA at baseline was not. Baseline factors independently associated with an unfavorable outcome were low/middle education level, comorbidity of the skeletal system, duration of knee symptoms of >3 months, bilateral knee symptoms, self-reported warm knee, history of nontraumatic knee symptoms, valgus alignment, pain at passive knee flexion/extension, and bony enlargement of the knee joint (AUC 0.80).
  
  
  CONCLUSIONS
  Nontraumatic knee symptoms in adults in general practice appear to become a chronic disorder in nearly half of the patients. The developed clinical prediction rule with 10 baseline prognostic factors can be used to select high-risk patients for an unfavorable outcome at long-term followup.
authors.affiliation: Erasmus MC University Medical Center, Rotterdam, The Netherlands. m.kastelein@erasmusmc.nl
authors.forename: Marlous
authors.initials: M
authors.lastname: Kastelein
authors.forename: Pim A J
authors.initials: PA
authors.lastname: Luijsterburg
authors.forename: Janneke N
authors.initials: JN
authors.lastname: Belo
authors.forename: Jan A N
authors.initials: JA
authors.lastname: Verhaar
authors.forename: Bart W
authors.initials: BW
authors.lastname: Koes
authors.forename: Sita M A
authors.initials: SM
authors.lastname: Bierma-Zeinstra
mesh_terms: D000328:Adult; D019645:Arthroplasty, Replacement, Knee; D018450:Disease Progression; D005260:Female; D058006:General Practice / Q000706:statistics & numerical data*; D006305:Health Status Indicators; D006801:Humans; D007717:Knee / Q000503:physiopathology* / Q000601:surgery; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009140:Musculoskeletal Diseases / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology / Q000601:surgery; D009426:Netherlands / Q000453:epidemiology; D016017:Odds Ratio; D010146:Pain / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology / Q000601:surgery; D010147:Pain Measurement; D011379:Prognosis; D011446:Prospective Studies; D020127:Recovery of Function; D018570:Risk Assessment; D012307:Risk Factors; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D013997:Time Factors