title: Physical activity and spatial differences in medial knee T1rho and t2 relaxation times in knee osteoarthritis.
abstract: METHODS
  Cross-sectional.
  
  
  OBJECTIVE
  To investigate the association between knee loading- related osteoarthritis (OA) risk factors (obesity, malalignment, and physical activity) and medial knee laminar (superficial and deep) T1rho and T2 relaxation times.
  
  
  BACKGROUND
  The interaction of various modifiable loading-related knee risk factors and cartilage health in knee OA is currently not well known.
  
  
  METHODS
  Participants with and without knee OA (n = 151) underwent magnetic resonance imaging at 3 T for superficial and deep cartilage T1rho and T2 magnetic resonance relaxation times in the medial femur (MF) and medial tibia (MT). Other variables included radiographic Kellgren-Lawrence (KL) grade, alignment, pain and symptoms using the Knee injury and Osteoarthritis Outcome Score, and physical activity using the International Physical Activity Questionnaire (IPAQ). Individuals with a KL grade of 4 were excluded. Group differences were calculated using 1-way analysis of variance, adjusting for age and body mass index. Linear regression models were created with age, sex, body mass index, alignment, KL grade, and the IPAQ scores to predict the laminar T1rho and T2 times.
  
  
  RESULTS
  Total IPAQ scores were the only significant predictors among the loading-related variables for superficial MF T1rho (P = .005), deep MT T1rho (P = .026), and superficial MF T2 (P = .049). Additionally, the KL grade predicted the superficial MF T1rho (P = .023) and deep MT T1rho (P = .022).
  
  
  CONCLUSIONS
  Higher physical activity levels and worse radiographic severity of knee OA, but not obesity or alignment, were associated with worse cartilage composition.
authors.affiliation: Musculoskeletal Quantitative Imaging Research Group, Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA.
authors.forename: Deepak
authors.initials: D
authors.lastname: Kumar
authors.forename: Richard B
authors.initials: RB
authors.lastname: Souza
authors.forename: Justin
authors.initials: J
authors.lastname: Singh
authors.forename: Nathaniel E
authors.initials: NE
authors.lastname: Calixto
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Nardo
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Link
authors.forename: Xiaojuan
authors.initials: X
authors.lastname: Li
authors.forename: Sharmila
authors.initials: S
authors.lastname: Majumdar
mesh_terms: D000368:Aged; D002358:Cartilage, Articular / Q000473:pathology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D009765:Obesity / Q000503:physiopathology; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology*; D011859:Radiography; D012307:Risk Factors
keywords: IPAQ; KL; cartilage; magnetic resonance imaging