title: Patients with hip osteoarthritis have a phenotype with high bone mass and low lean body mass.
abstract: BACKGROUND
  Although hip osteoarthritis (OA) is common, its etiology is poorly understood. Specifically, it is not known whether hip OA is associated with abnormal relationships among the anthropometric and musculoskeletal characteristics that are associated with OA in general.
  
  
  OBJECTIVE
  We asked whether patients with primary hip OA have a phenotype with higher bone mineral density (BMD), higher BMI, larger skeletal size, lower lean body mass, and higher fat content.
  
  
  METHODS
  We included 30 women and 32 men (mean age, 66 years; range, 42-84 years) with primary hip OA and 96 women and 91 men as control subjects. Dual energy x-ray absorptiometry was used to measure total body BMD (g/cm(2)), femoral neck width (cm), fat and lean mass (%), and BMI (kg/m(2)). Z scores were calculated for each individual. Data are presented as means with 95% CI.
  
  
  RESULTS
  Women with hip OA had the following Z scores: total body BMD 0.6 (0.3, 1.0); BMI 0.6 (0.2, 1.0); femoral neck width 0.2 (-0.6, 1.0); percent total body lean mass -0.9 (-1.2, -0.5); and percent total body fat mass 0.6 (0.2, 0.9). Men with hip OA had the following mean Z scores: total body BMD 0.5 (0.0, 1.0); BMI 0.8 (0.3, 1.3); femoral neck width 0.4 (0.01, 0.9); percent total body lean mass -0.8 (-1.1, -0.5); and percent total body fat mass 0.5 (0.2, 0.8).
  
  
  CONCLUSIONS
  Women and men with idiopathic hip OA have a phenotype with higher BMD, higher BMI, proportionally higher fat mass, and proportionally lower lean body mass. Men also have a larger skeletal size.
  
  
  CONCLUSIONS
  A higher BMD may lead to a stiffer bone and a proportionally lower lean body mass to lower joint-protective ability, both traits probably predisposing for hip OA.
authors.affiliation: Clinical and Molecular Osteoporosis Research Unit, Departments of Orthopedics and Clinical Sciences, Skåne University Hospital, Lund University, 205 02, Malmö, Sweden, magnus.karlsson@med.lu.se.
authors.forename: Magnus K
authors.initials: MK
authors.lastname: Karlsson
authors.forename: Håkan
authors.initials: H
authors.lastname: Magnusson
authors.forename: Maria C
authors.initials: MC
authors.lastname: Cöster
authors.forename: Tord
authors.initials: T
authors.lastname: Vonschewelov
authors.forename: Caroline
authors.initials: C
authors.lastname: Karlsson
authors.forename: Björn E
authors.initials: BE
authors.lastname: Rosengren
mesh_terms: D015502:Absorptiometry, Photon; D050154:Adiposity; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D015519:Bone Density; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D005260:Female; D005272:Femur Neck / Q000000981:diagnostic imaging / Q000503:physiopathology*; D006801:Humans; D016014:Linear Models; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D015207:Osteoarthritis, Hip / Q000000981:diagnostic imaging / Q000209:etiology* / Q000503:physiopathology; D010641:Phenotype; D012307:Risk Factors; D012737:Sex Factors