title: Relationship between knee kinetics during jumping tasks and knee articular cartilage MRI T1rho and T2 relaxation times.
abstract: BACKGROUND
  Articular cartilage of young healthy individuals is dynamic and responsive to loading behaviors. The purpose of this study was to evaluate the relationship of cartilage T(1ρ) and T(2) relaxation times with loading kinetics during jumping tasks in healthy young individuals.
  
  
  METHODS
  Fourteen healthy subjects underwent: 1) motion analysis while performing a unilateral hopping task and bilateral drop jumping task; and 2) quantitative imaging using a 3 Tesla MRI for T(1ρ) and T(2) relaxation time analysis. Three dimensional net joint moments and angular impulse was calculated using standard inverse dynamics equations. Average T(1ρ) and T(2) relaxation times and medial-lateral ratios for each were calculated. Multiple regression was used to identify predictors of cartilage relaxation times.
  
  
  RESULTS
  Average knee flexion moment during hopping was observed to best predict overall T(1ρ) (R(2)=.185) and T(2) (R(2)=.154) values. Peak knee adduction moment during a drop jump was the best predictor of the T(1ρ) medial-lateral ratio (R(2)=.220). The T(2) medial-lateral ratio was best predicted by average internal rotation moment during the drop jump (R(2)=.174).
  
  
  CONCLUSIONS
  These data suggest that loads across the knee may affect the biochemistry of the cartilage. In young healthy individuals, higher flexion moments were associated with decreased T(1ρ) and T(2) values, suggesting a potentially beneficial effect. The medial-to-lateral ratio of T(1ρ) and T(2) times appears to be related to the frontal and transverse plane joint mechanics. These data offer promising findings of potentially modifiable parameters associated with cartilage composition.
authors: Department of Physical Therapy and Rehabilitation Science, University of California, San Francisco, San Francisco, CA 94107, USA. richard.souza@ucsf.edu
authors: Richard B
authors: RB
authors: Souza
authors: Charles
authors: C
authors: Fang
authors: Anthony
authors: A
authors: Luke
authors: Samuel
authors: S
authors: Wu
authors: Xiaojuan
authors: X
authors: Li
authors: Sharmila
authors: S
authors: Majumdar
mesh_terms: D000328:Adult; D002358:Cartilage, Articular / Q000737:chemistry* / Q000502:physiology*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000033:anatomy & histology / Q000502:physiology*; D008124:Locomotion / Q000502:physiology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D016059:Range of Motion, Articular / Q000502:physiology*