title: A large infrapatellar fat pad protects against knee pain and lateral tibial cartilage volume loss.
abstract: BACKGROUND
  The infrapatellar fat pad (IPFP) is commonly resected during knee joint arthroplasty, but the ramifications of doing so are unclear. This longitudinal study determined whether the size of the IPFP (maximum cross-sectional area (CSA)) was associated with knee cartilage loss and the development of knee pain in adults without knee osteoarthritis (OA).
  
  
  METHODS
  A total of 297 adults without American College of Rheumatology clinical criteria for a diagnosis of knee OA were recruited. Knee MRI was performed at baseline and an average of 2.3 years later. IPFP maximal CSA and tibial cartilage volume were measured from MRI. A large and small IPFP were defined by the median split, with a large IPFP defined by being in the highest 50%. Body composition was performed at baseline using bio-impedance. Knee pain was assessed at follow-up using the Western Ontario and McMaster University Osteoarthritis Index (WOMAC).
  
  
  RESULTS
  A larger IPFP at baseline was associated with reduced knee pain at follow-up (OR 0.5, 95% CI: 0.3 to 0.9, p = 0.02) and lateral tibial cartilage volume loss (β: -0.9% (95% CI: -1.6, -0.1%) per annum, p = 0.03). The maximal CSA of the IPFP was predominantly located in the lateral (54.2%), rather than the medial tibiofemoral compartment (1.7%). Male gender (OR 12.0, 95% CI: 6.5 to 22.0, p < 0.001) and fat free mass (OR 1.15, 95% CI 1.04 to 1.28, p = 0.007) were both associated with a large IPFP.
  
  
  CONCLUSIONS
  A larger IPFP predicts reduced lateral tibial cartilage volume loss and development of knee pain and mechanistically might function as a local shock-absorber. The lack of association between measures of adiposity and the size of the IPFP might suggest that the IPFP size is not simply a marker of systemic obesity.
authors.affiliation: Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University, Alfred Hospital, Melbourne, VIC, 3004, Australia. andrew.teichtahl@monash.edu.|Baker IDI Heart and Diabetes Institute, Commercial Road, Melbourne, VIC, 3004, Australia. andrew.teichtahl@monash.edu.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Teichtahl
authors.affiliation: Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University, Alfred Hospital, Melbourne, VIC, 3004, Australia. ewul1@student.monash.edu.
authors.forename: Ema
authors.initials: E
authors.lastname: Wulidasari
authors.affiliation: Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University, Alfred Hospital, Melbourne, VIC, 3004, Australia. sharmayne.brady@monash.edu.
authors.forename: Sharmayne R E
authors.initials: SR
authors.lastname: Brady
authors.affiliation: Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University, Alfred Hospital, Melbourne, VIC, 3004, Australia. yuanyuan.wang@monash.edu.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University, Alfred Hospital, Melbourne, VIC, 3004, Australia. anita.wluka@monash.edu.
authors.forename: Anita E
authors.initials: AE
authors.lastname: Wluka
authors.affiliation: Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University, Alfred Hospital, Melbourne, VIC, 3004, Australia. changhai.ding@utas.edu.au.|Menzies Research Institute Tasmania, University of Tasmania, Hobart, TAS, 7000, Australia. changhai.ding@utas.edu.au.
authors.forename: Changhai
authors.initials: C
authors.lastname: Ding
authors.affiliation: Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University, Alfred Hospital, Melbourne, VIC, 3004, Australia. graham.giles@cancervic.org.au.|Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Carlton, VIC, 3053, Australia. graham.giles@cancervic.org.au.|Cancer Epidemiology Centre, Cancer Council Victoria, Melbourne, VIC, 3004, Australia. graham.giles@cancervic.org.au.
authors.forename: Graham G
authors.initials: GG
authors.lastname: Giles
authors.affiliation: Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University, Alfred Hospital, Melbourne, VIC, 3004, Australia. flavia.cicuttini@monash.edu.
authors.forename: Flavia M
authors.initials: FM
authors.lastname: Cicuttini
mesh_terms: D000273:Adipose Tissue / Q000473:pathology / Q000503:physiopathology*; D000328:Adult; D000368:Aged; D002358:Cartilage, Articular / Q000473:pathology / Q000503:physiopathology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000473:pathology / Q000503:physiopathology*; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000473:pathology / Q000503:physiopathology*