title: Asymmetric loading and bone mineral density at the asymptomatic knees of patients with unilateral hip osteoarthritis.
abstract: OBJECTIVE
  In patients with unilateral end-stage hip osteoarthritis (OA), the contralateral knee is known to be at greater risk for end-stage knee OA compared to the ipsilateral (i.e., same-side) knee. The contralateral knee is known to have increased dynamic joint loads compared to the ipsilateral knee. The present study was undertaken to examine patients who had unilateral hip OA but who did not have symptoms of knee OA, in order to detect early asymmetries in knee loading.
  
  
  METHODS
  Data on 62 patients with unilateral hip OA were evaluated. Patients underwent gait analyses of dynamic knee loads as well as dual x-ray absorptiometry for determination of bone mineral density (BMD) in both knees. Differences between knees were compared.
  
  
  RESULTS
  Peak dynamic knee loads were significantly higher at the contralateral knee compared to the ipsilateral knee (mean ± SD 2.46 ± 0.71 percent of body weight × height versus 2.23 ± 0.81 percent of body weight × height; P = 0.029). Similarly, medial compartment tibial BMD was significantly higher in the contralateral knee compared to the ipsilateral knee (mean ± SD 0.897 ± 0.208 gm/cm(2) versus 0.854 ± 0.206 gm/cm(2); P = 0.033). Interestingly, there was a direct correlation between the contralateral:ipsilateral dynamic knee load and contralateral:ipsilateral medial compartment tibial BMD (ρ = 0.287, P = 0.036).
  
  
  CONCLUSIONS
  The risk of developing progressive symptomatic OA in contralateral knees is higher compared to the risk in ipsilateral knees in patients with unilateral hip OA. The present study demonstrates that loading and structural asymmetries appear early in the disease course, while the knees are still asymptomatic. These early biomechanical asymmetries may have corresponding long-term consequences, providing further evidence for the potential role of loading in OA onset and progression.
authors: Section of Rheumatology, Rush Medical College, Chicago, Illinois 60612-3862, USA. najia_shakoor@rush.edu
authors: Najia
authors: N
authors: Shakoor
authors: Anisha
authors: A
authors: Dua
authors: Laura E
authors: LE
authors: Thorp
authors: Rachel A
authors: RA
authors: Mikolaitis
authors: Markus A
authors: MA
authors: Wimmer
authors: Kharma C
authors: KC
authors: Foucher
authors: Louis F
authors: LF
authors: Fogg
authors: Joel A
authors: JA
authors: Block
mesh_terms: D015502:Absorptiometry, Photon; D000368:Aged; D001696:Biomechanical Phenomena; D015519:Bone Density / Q000502:physiology*; D018450:Disease Progression; D005260:Female; D005684:Gait / Q000502:physiology; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D015207:Osteoarthritis, Hip / Q000150:complications* / Q000503:physiopathology*; D020370:Osteoarthritis, Knee / Q000453:epidemiology* / Q000503:physiopathology; D012307:Risk Factors; D016474:Weight-Bearing / Q000502:physiology