title: Physical activity in relation to knee cartilage T2 progression measured with 3 T MRI over a period of 4 years: data from the Osteoarthritis Initiative.
abstract: OBJECTIVE
  The purpose of this study was to analyze the longitudinal association between physical activity levels and early degenerative cartilage changes in the knee, measured using T2 relaxation times over a period of 4 years in individuals without clinical or radiographic evidence of OA.
  
  
  METHODS
  Cartilage T2 was measured at baseline and after 2 and 4 years in 205 subjects aged 45-60 years from the Osteoarthritis Initiative (OAI) incidence and normal cohorts with no knee pain (Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score of zero), and a Kellgren Lawrence (KL) score of <2 at baseline. Physical activity was scored using the Physical Activity Scale for the Elderly (PASE) questionnaire, which was obtained yearly over 4 years. The relationship between physical activity and T2 was studied using a mixed model linear regression, including random effects, and adjusted for age, sex, and body mass index (BMI).
  
  
  RESULTS
  T2 values for all PASE tertiles progressed over the 4-year period. T2 progression was increased in the highest tertile of physical activity compared to the mid-tertile at the medial tibia (MT) (P = 0.041), patella (Pat) (P = 0.019), and average T2 of all knee compartments combined (P = 0.033). Subjects with the lowest 15% PASE scores showed significantly higher T2 progression compared to the mid-level physical activity group at the lateral femur (LF) (P = 0.025), lateral tibia (LT) (P = 0.043), medial femur (MF) (P = 0.044), tibiofemoral compartment (P = 0.017), patellofemoral compartment (P = 0.016), lateral compartments (P = 0.003), and average of all compartments (P = 0.043).
  
  
  CONCLUSIONS
  High and very low PASE scores were associated with greater progression of cartilage T2 measurements in asymptomatic, middle-aged individuals, suggesting accelerated cartilage matrix biochemical degeneration over time.
authors.affiliation: Musculoskeletal and Quantitative Imaging Research, Department of Radiology and Biomedical Imaging, University of California San Francisco, 185 Berry Street, Suite 350, San Francisco, CA 94107, USA. Electronic address: wilson.lin@ucsf.edu.
authors.forename: W
authors.initials: W
authors.lastname: Lin
authors.forename: H
authors.initials: H
authors.lastname: Alizai
authors.forename: G B
authors.initials: GB
authors.lastname: Joseph
authors.forename: W
authors.initials: W
authors.lastname: Srikhum
authors.forename: M C
authors.initials: MC
authors.lastname: Nevitt
authors.forename: J A
authors.initials: JA
authors.lastname: Lynch
authors.forename: C E
authors.initials: CE
authors.lastname: McCulloch
authors.forename: T M
authors.initials: TM
authors.lastname: Link
mesh_terms: D002358:Cartilage, Articular / Q000473:pathology* / Q000503:physiopathology; D018450:Disease Progression; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000209:etiology / Q000473:pathology* / Q000503:physiopathology; D011859:Radiography; D012307:Risk Factors; D012720:Severity of Illness Index
keywords: Cartilage; Knee; MRI; Physical activity; T2 relaxation time