title: Bone marrow lesions identified by MRI in knee osteoarthritis are associated with locally increased bone mineral density measured by QCT.
abstract: OBJECTIVE
  Bone marrow lesions (BMLs) in the knee are associated with pain and compartment-specific joint space narrowing. However, the correlation of BMLs with bone mineral density (BMD) has rarely been investigated. The aim of the present study was to examine whether BMD in BMLs is altered compared to the surrounding bone.
  
  
  METHODS
  Thirty-four BMLs detected in osteoarthritis (OA) knees (KL grade 2 and 3) of 26 patients were investigated. A 3D-segmentation was used to determine BML volumes of interest (VOI) and their surrounding bone in MR images. These VOIs were registered to corresponding single-energy QCT images and a BMD analysis was performed. The same VOIs were transferred to control datasets (19 OA patients without BMLs) by an elastic registration, where the BMD analysis was repeated. To account for the dependence of bone marrow composition on BMD measures derived using single-energy QCT, simulations were performed to evaluate how changing fat-water compositions likely occurring with BML development may influence BMD measures and observed BMD differences between patients with and without BMLs. The association between loading in the knee and the occurrence of BMLs was investigated by medial to lateral (M:L) BMD ratios.
  
  
  RESULTS
  BMD was significantly increased at BML locations, even with a fat-to-water conversion rate of 39%. The M:L BMD ratio was significantly increased in bones with medial BMLs.
  
  
  CONCLUSIONS
  BMD was examined exactly at BML locations and surrounding bone using highly accurate segmentation and registration methods. BMD was significantly increased at BML locations (P < 0.05).
authors.affiliation: Institute of Medical Physics, University of Erlangen-Nuernberg, Erlangen, Germany. Torsten.Lowitz@imp.uni-erlangen.de
authors.forename: T
authors.initials: T
authors.lastname: Lowitz
authors.forename: O
authors.initials: O
authors.lastname: Museyko
authors.forename: V
authors.initials: V
authors.lastname: Bousson
authors.forename: L
authors.initials: L
authors.lastname: Laouisset
authors.forename: W A
authors.initials: WA
authors.lastname: Kalender
authors.forename: J-D
authors.initials: JD
authors.lastname: Laredo
authors.forename: K
authors.initials: K
authors.lastname: Engelke
mesh_terms: D000368:Aged; D015519:Bone Density / Q000502:physiology*; D001855:Bone Marrow Diseases / Q000150:complications / Q000175:diagnosis*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000150:complications / Q000473:pathology*; D014057:Tomography, X-Ray Computed / Q000379:methods