title: The epidemiology of symptomatic midfoot osteoarthritis in community-dwelling older adults: cross-sectional findings from the Clinical Assessment Study of the Foot.
abstract: BACKGROUND
  The foot is largely overlooked in calls for better characterisation of clinical phenotypes in osteoarthritis (OA). Yet the midfoot complex in particular has the potential to provide important insights into OA pathogenesis given its central role in lower limb load transmission and alignment. Its recent inclusion in radiographic atlases has paved the way for international studies. In this UK study, we provide the first comprehensive account of the descriptive epidemiology of symptomatic midfoot OA.
  
  
  METHODS
  Participants aged ≥50 years registered with four general practices were recruited via a mailed health survey (n = 5109 responders) and research clinic (n = 560 responders). Symptomatic midfoot OA was defined as midfoot pain in the last 4 weeks, combined with radiographic OA in one or more joints (1st and 2nd cuneometatarsal, navicular first cuneiform and talonavicular joints) graded from weight-bearing dorso-plantar and lateral radiographs using a validated atlas. Prevalence estimates, overall and stratified by age, gender, and socio-economic class, were derived using multiple imputation and weighted logistic regression. Associations between symptomatic midfoot OA and current body mass index, previous injury, history of high-heeled footwear, nodal interphalangeal joint OA and patterns of comorbidity were estimated using binary logistic regression. Healthcare use was summarised.
  
  
  RESULTS
  Symptomatic midfoot OA was present in 12.0% (95 % CI: 10.9, 13.2) of the population aged over 50 years. Higher occurrence was observed in females, adults aged over 75 years, and those in intermediate/routine occupational classes. Obesity, previous foot/ankle injury, and pain in other weight-loaded joints, but not high-heeled footwear or nodal interphalangeal joint OA, were associated with increased risk of symptomatic midfoot OA. Persons with symptomatic midfoot OA were also more likely to report multiple non-musculoskeletal comorbidities, including diabetes. In the previous 12 months, the proportions consulting a general practitioner, physiotherapist or podiatrist/chiropodist about foot pain were 46.2%, 18.5% and 47.9% respectively. A total of 64.7% had used oral analgesia in the past month for foot pain (36.1% paracetamol, 31.9% mild/moderate opioids, 27.7% NSAIDs).
  
  
  CONCLUSIONS
  Our study confirms that symptomatic OA frequently affects the midfoot. The patterns of associations are interpreted as being largely consistent with the role of mechanical factors in its pathogenesis.
authors.affiliation: Arthritis Research UK Primary Care Centre, Research Institute for Primary Care and Health Sciences, Keele University, Keele, Staffordshire, ST5 5BG, UK. m.thomas@keele.ac.uk.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Thomas
authors.affiliation: Arthritis Research UK Primary Care Centre, Research Institute for Primary Care and Health Sciences, Keele University, Keele, Staffordshire, ST5 5BG, UK. g.m.peat@keele.ac.uk.
authors.forename: George
authors.initials: G
authors.lastname: Peat
authors.affiliation: Arthritis Research UK Primary Care Centre, Research Institute for Primary Care and Health Sciences, Keele University, Keele, Staffordshire, ST5 5BG, UK. t.rathod@keele.ac.uk.
authors.forename: Trishna
authors.initials: T
authors.lastname: Rathod
authors.affiliation: Arthritis Research UK Primary Care Centre, Research Institute for Primary Care and Health Sciences, Keele University, Keele, Staffordshire, ST5 5BG, UK. m.marshall@keele.ac.uk.
authors.forename: Michelle
authors.initials: M
authors.lastname: Marshall
authors.affiliation: Musculoskeletal Research Unit, School of Clinical Sciences, University of Bristol, Bristol, BS10 5NB, UK. a.j.moore@bristol.ac.uk.
authors.forename: Andrew
authors.initials: A
authors.lastname: Moore
authors.affiliation: Arthritis Research UK Primary Care Centre, Research Institute for Primary Care and Health Sciences, Keele University, Keele, Staffordshire, ST5 5BG, UK. h.menz@latrobe.edu.au.|Lower Extremity and Gait Studies Program, School of Allied Health, La Trobe University, Bundoora, Victoria, 3086, Australia. h.menz@latrobe.edu.au.
authors.forename: Hylton B
authors.initials: HB
authors.lastname: Menz
authors.affiliation: Arthritis Research UK Primary Care Centre, Research Institute for Primary Care and Health Sciences, Keele University, Keele, Staffordshire, ST5 5BG, UK. e.roddy@keele.ac.uk.
authors.forename: Edward
authors.initials: E
authors.lastname: Roddy
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D005260:Female; D005528:Foot / Q000000981:diagnostic imaging*; D006801:Humans; D057187:Independent Living; D008297:Male; D008875:Middle Aged; D010003:Osteoarthritis / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D010146:Pain / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D011859:Radiography; D016474:Weight-Bearing / Q000502:physiology