title: Frequency and spatial distribution of cartilage thickness change in knee osteoarthritis and its relation to clinical and radiographic covariates - data from the osteoarthritis initiative.
abstract: OBJECTIVE
  Estimate the frequency and spatial location of rapid femorotibial cartilage thinning or thickening in knees with, or at risk of, osteoarthritis (OA) and examine their association with clinical and radiographic covariates.
  
  
  METHODS
  Knee cartilage thickness change over 12 months was measured using magnetic resonance imaging in the right knee of 757 Osteoarthritis Initiative (OAI) participants that had radiographic findings of osteophytes or joint space narrowing (JSN). Thickness changes in individual knees were classified as having rapid thinning or thickening or no detectable OA-related change when compared to asymptomatic OAI Control cohort knees.
  
  
  RESULTS
  Cartilage thinning, found in 18.5% of subjects, was more frequent in knees with OAI calculated Kellgren-Lawrence grade (cKLG) > 2 (P < 0.001) and with frequent pain (P = 0.047). No link was found between body mass index, sex, and age and cartilage thinning (P > 0.15). The percent of knees with thickening was small (4.4%), but greater in knees with frequent pain (P = 0.02). Rapid thinning was most common in the central (36.4%) and external (32.1%) subregions of the medial weight-bearing femur. Mean cartilage loss in rapidly thinning subregions ranged from 11.2%/y to 24.6%/y. Knees with cKLG > 2, but classified as having no detectable OA-related change had mean cartilage loss rates significantly >0 (0.4%/y-1.3%/y) in 10 subregions.
  
  
  CONCLUSIONS
  Most observed subregional changes in OA knees were indistinguishable from changes found in an asymptomatic cohort, but a fraction of subregions showed rapid progression. The relative frequency of rapid thinning increases when cKLG > 2, a classification closely associated with JSN and/or frequent knee pain are present.
authors.affiliation: StatAnswers Consulting LLC, San Diego, CA, USA. robert.j.buck@gmail.com
authors.forename: R J
authors.initials: RJ
authors.lastname: Buck
authors.forename: W
authors.initials: W
authors.lastname: Wirth
authors.forename: D
authors.initials: D
authors.lastname: Dreher
authors.forename: M
authors.initials: M
authors.lastname: Nevitt
authors.forename: F
authors.initials: F
authors.lastname: Eckstein
mesh_terms: D000367:Age Factors; D000368:Aged; D015992:Body Mass Index; D002358:Cartilage, Articular / Q000000981:diagnostic imaging / Q000473:pathology*; D016022:Case-Control Studies; D018450:Disease Progression; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000473:pathology*; D010146:Pain; D011859:Radiography; D012307:Risk Factors; D012737:Sex Factors