title: Delayed gadolinium-enhanced magnetic resonance imaging of cartilage in knee osteoarthritis: findings at different radiographic stages of disease and relationship to malalignment.
abstract: OBJECTIVE
  Delayed gadolinium-enhanced magnetic resonance imaging (MRI) of cartilage (dGEMRIC) is used to examine the distribution of glycosaminoglycan in cartilage. This study sought to characterize dGEMRIC in the evaluation of knee osteoarthritis (OA) according to various radiographically determined disease parameters, and to examine the relationship between alignment of the knee joint and the lateral:medial dGEMRIC ratio.
  
  
  METHODS
  Thirty-one patients with knee OA underwent MRI with a dGEMRIC protocol at 1.5T. Semiflexed knee radiographs and full-limb radiographs were also obtained for assessment of alignment.
  
  
  RESULTS
  Compartments of the knee joint without joint space narrowing had a higher dGEMRIC index than those with any level of narrowing (mean 408 msec versus 365 msec; P = 0.001). In knees with 1 unnarrowed (spared) and 1 narrowed (diseased) compartment, the dGEMRIC index was greater in the spared versus the diseased compartment (mean 395 msec versus 369 msec; P = 0.001). In spared compartments, there was a trend toward a lower dGEMRIC index with increasing Kellgren/Lawrence (K/L) radiographic severity grade; the spared compartments of knees with a K/L grade 2 had a higher dGEMRIC index than those of knees with a K/L grade 4 (mean 425 msec versus 371 msec; P < 0.05). There was a range of dGEMRIC values in the spared compartments within a given K/L grade, demonstrating biochemical differentiation of disease in radiographically comparable compartments. Almost all compartments with narrowing had dGEMRIC indices of <400 msec. Valgus-aligned knees tended to have lower dGEMRIC values laterally, and varus-aligned knees tended to have lower dGEMRIC values medially; as a continuous variable, alignment correlated with the lateral:medial dGEMRIC ratio (Pearson's R = 0.43, P = 0.02).
  
  
  CONCLUSIONS
  The biochemical information provided by dGEMRIC scans may augment radiography by improving the differentiation of disease status within a given radiographic grade, especially in early OA.
authors.affiliation: Beth Israel Deaconess Medical Center and Harvard Medical School, #4 Blackfan Circle, Boston, MA 02115, USA.
authors.forename: Ashley
authors.initials: A
authors.lastname: Williams
authors.forename: Leena
authors.initials: L
authors.lastname: Sharma
authors.forename: Charles A
authors.initials: CA
authors.lastname: McKenzie
authors.forename: Pottumarthi V
authors.initials: PV
authors.lastname: Prasad
authors.forename: Deborah
authors.initials: D
authors.lastname: Burstein
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D017760:Bone Malalignment / Q000175:diagnosis* / Q000503:physiopathology; D002358:Cartilage, Articular / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology*; D003287:Contrast Media; D005260:Female; D019786:Gadolinium DTPA; D006025:Glycosaminoglycans / Q000378:metabolism; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000378:metabolism; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000175:diagnosis* / Q000378:metabolism; D011859:Radiography
chemical_list: D003287:Contrast Media; D006025:Glycosaminoglycans; D019786:Gadolinium DTPA