title: Association of Body Mass Index With Incidence and Progression of Knee Effusion on Magnetic Resonance Imaging and on Knee Examination.
abstract: OBJECTIVE
  To determine the association of body mass index (BMI) with incidence and progression of knee effusion on magnetic resonance imaging (MRI) and physical examination (PE) in a longitudinal cohort with knee pain.
  
  
  METHODS
  A population-based cohort was assessed at baseline and 3 years (n = 163). BMI was categorized as normal (<25), overweight (25-29.9), and obese (≥30). Knee effusion was graded as 0-3 (absent/mild/moderate/severe) on MRI and 0-1 (absent/present) on PE. Progression of MRI effusion (MRIeff ) was an increase of ≥1 grade in those with grade 1 or 2 at baseline. Incident MRIeff and PE effusion (PEeff ) were any effusion at followup (>0) in those with grade 0 at baseline. A second type of incident MRIeff was effusion grade ≥2 at followup in those with grade <2 at baseline. Exponential regression analysis was used, adjusted for age, sex, and radiographic severity.
  
  
  RESULTS
  Incident MRIeff ≥1, incident MRIeff ≥2, incident PEeff , and progression of MRIeff were seen in 14 of 73 (19%), 18 of 140 (13%), 26 of 127 (20%), and 18 of 86 (21%), respectively. There was a borderline statistical association of obesity with progression of MRIeff (hazard ratio [HR] 3.3 [95% confidence interval (95% CI) 1.0-11.2]) and with incident MRIeff ≥2 (HR 3.4 [95% CI 1.0-11.5]). BMI was not associated with incident MRIeff ≥1 (HR overweight 1.1 [95% CI 0.3-3.6], obese 1.0 [95% CI 0.2-5.0]). Overweight was associated with incident PEeff (HR 4.5 [95% CI 1.4-14.2]), while obesity was not statistically significant (HR 3.1 [95% CI 0.9-11.1]).
  
  
  CONCLUSIONS
  Obesity was a risk factor for incident and progressive knee effusion in this population-based cohort. These findings highlight an important link between obesity and inflammation in knee osteoarthritis.
authors.affiliation: University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Amy
authors.initials: A
authors.lastname: Hung
authors.affiliation: Arthritis Research Canada, Vancouver, British Columbia, Canada.
authors.forename: Eric C
authors.initials: EC
authors.lastname: Sayre
authors.affiliation: Boston University, Boston, Massachusetts.
authors.forename: Ali
authors.initials: A
authors.lastname: Guermazi
authors.affiliation: University of British Columbia and Arthritis Research Canada, Vancouver, British Columbia, Canada.
authors.forename: John M
authors.initials: JM
authors.lastname: Esdaile
authors.affiliation: University of British Columbia and Arthritis Research Canada, Vancouver, British Columbia, Canada.
authors.forename: Jacek A
authors.initials: JA
authors.lastname: Kopec
authors.affiliation: University of British Columbia and CIHR Canadian HIV Trials Network, Vancouver, British Columbia, Canada.
authors.forename: Anona
authors.initials: A
authors.lastname: Thorne
authors.affiliation: University of British Columbia and Centre for Health Evaluation and Outcome Sciences, Vancouver, British Columbia, Canada.
authors.forename: Joel
authors.initials: J
authors.lastname: Singer
authors.affiliation: University of British Columbia and CIHR Canadian HIV Trials Network, Vancouver, British Columbia, Canada.
authors.forename: Hubert
authors.initials: H
authors.lastname: Wong
authors.affiliation: University of British Columbia and Vancouver General Hospital.
authors.forename: Savvas
authors.initials: S
authors.lastname: Nicolaou
authors.affiliation: University of British Columbia and Arthritis Research Canada, Vancouver, British Columbia, Canada.
authors.forename: Jolanda
authors.initials: J
authors.lastname: Cibere
mesh_terms: D000328:Adult; D000368:Aged; D018771:Arthralgia / Q000453:epidemiology* / Q000473:pathology / Q000503:physiopathology; D001696:Biomechanical Phenomena; D015992:Body Mass Index; D001955:British Columbia / Q000453:epidemiology; D018450:Disease Progression; D005260:Female; D006801:Humans; D015994:Incidence; D007719:Knee Joint / Q000473:pathology* / Q000503:physiopathology*; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000175:diagnosis / Q000453:epidemiology*; D020370:Osteoarthritis, Knee / Q000453:epidemiology* / Q000473:pathology / Q000503:physiopathology; D010147:Pain Measurement; D011237:Predictive Value of Tests; D012307:Risk Factors; D012720:Severity of Illness Index