title: Knee disorders in primary care: design and patient selection of the HONEUR knee cohort.
abstract: BACKGROUND
  Knee complaints are a frequent reason for consultation in general practice. These patients constitute a specific population compared to secondary care patients. However, information to base treatment decisions on is generally derived from specialistic settings. Our cohort study is aimed at collecting knowledge about prognosis and prognostic factors of knee complaints presented in a primary care setting. This paper describes the methods used for data collection, and discusses potential selectiveness of patient recruitment.
  
  
  METHODS
  This is a descriptive prospective cohort study with one-year follow-up. 40 Dutch GPs recruited consecutive patients with incident knee complaints aged 12 years and above from October 2001 to October 2003. Patients were assessed with questionnaires and standardised physical examinations. Additional measurements of subgroups included MRI for recent knee traumas and device assessed function measurements for non-traumatic patients. After the inclusion period we retrospectively searched the computerized medical files of participating GPs to obtain a sample to determine possible selective recruitment. We assessed differences in proportions of gender, traumatic onset of injury and age groups between participants and non-participants using Odds Ratios (OR) and 95% confidence intervals.
  
  
  RESULTS
  We recruited 1068 patients. In a sample of 310 patients visiting the GP, we detected some selective recruitment, indicating an underrepresentation of patients aged 12 to 35 years (OR 1.70; 1.15-2.77), especially among men (OR 2.16; 1.12-4.18). The underrepresentation of patients with traumatic onset of injury was not statistically significant.
  
  
  CONCLUSIONS
  This cohort is unique in its size, setting, and its range of both age and type of knee complaints. We believe the detected selective recruitment is unlikely to introduce significant bias, as the cohort will be divided into subgroups according to age group or traumatic onset of injury for future analyses. However, the underrepresentation of men in the age group of 12 to 35 years of age warrants caution. Based on the available data, we believe our cohort is an acceptable representation of patients with new knee complaints consulting the GP, and we expect no problems with extrapolation of the results to the general Dutch population.
authors.affiliation: Department of General Practice, Erasmus University Medical Centre, PO Box 1738, 3000 DR Rotterdam, The Netherlands. e.heintjes@erasmusmc.nl
authors.forename: Edith M
authors.initials: EM
authors.lastname: Heintjes
authors.forename: Marjolein Y
authors.initials: MY
authors.lastname: Berger
authors.forename: Bart W
authors.initials: BW
authors.lastname: Koes
authors.forename: Sita M
authors.initials: SM
authors.lastname: Bierma-Zeinstra
mesh_terms: D000293:Adolescent; D000328:Adult; D015331:Cohort Studies; D003625:Data Collection; D005260:Female; D006801:Humans; D007592:Joint Diseases / Q000628:therapy*; D007719:Knee Joint; D008297:Male; D009426:Netherlands; D018579:Patient Selection; D011320:Primary Health Care; D011379:Prognosis