title: Body mass index and knee osteoarthritis risk: a dose-response meta-analysis.
abstract: OBJECTIVE
  Evidence shows obesity is an important risk factor for knee osteoarthritis (OA). However, the dose-response relationship between body mass index (BMI) and knee OA risk is unclear. The purpose of the current study is to establish a nonlinear dose-response relationship between BMI and risk of knee OA.
  
  
  METHODS
  The electronic database of PubMed, Web of Science, and translating research into practice (TRIP) database were searched. Observational studies for BMI and knee OA risk were included. Restricted cubic splines and generalized least-squares regression methods were used to model a potential curvilinear relationship and to make a dose-response meta-analysis.
  
  
  RESULTS
  A total of 12 studies were included in the meta-analysis. A non-linear dose-response association between BMI and risk of knee OA was significant (P = 0.001). The relative risks were 1.59 (95% CI: 1.34-1.81), 3.55 (95% CI: 2.51-5.11), and 7.45 (95% CI: 4.19-13.13) when BMI was at the point of 25, 30, and 35 kg/m(2) compared with reference (22.5 kg/m(2) , the median value of the lowest category), respectively. Non-linear dose-response association was also significant in male and female subgroup. In male subgroup, the relative risks were 1.39 (95% CI: 0.99-1.92), 3.41 (95% CI: 2.07-5.48), and 5.71 (95% CI: 3.12-9.95) when BMI was at the point of 25, 30, and 32.5 kg/m(2) compared with reference, respectively. In female subgroup, the relative risks were 1.72 (95% CI: 1.51-1.99), 3.51 (95% CI: 2.65-4.51), and 4.72 (95% CI: 3.25-6.91) compared with reference when BMI was at the point of 25, 30, and 32.5 kg/m(2) compared with reference, respectively. Modest publication bias was found in the meta-analysis. However, sensitivity analysis showed a high stability for the result.
  
  
  CONCLUSIONS
  The meta-analysis indicated that knee OA risk increased almost exponentially according with the increase of body mass index. Knee OA prevention will benefit from weight control.
authors.affiliation: Department of Orthopaedics, Affiliated Hospital of Nantong University, Nantong, Jiangsu, People's Republic of China.
authors.forename: Zhen-Yu
authors.initials: ZY
authors.lastname: Zhou
authors.forename: Ya-Ke
authors.initials: YK
authors.lastname: Liu
authors.forename: Hong-Lin
authors.initials: HL
authors.lastname: Chen
authors.forename: Fan
authors.initials: F
authors.lastname: Liu
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications / Q000453:epidemiology; D020370:Osteoarthritis, Knee / Q000453:epidemiology* / Q000209:etiology*; D012307:Risk Factors; D055815:Young Adult