title: Changes in MR relaxation times of the meniscus with acute loading: an in vivo pilot study in knee osteoarthritis.
abstract: OBJECTIVE
  To prospectively evaluate changes in T1ρ and T2 relaxation times in the meniscal body with acute loading using MRI in osteoarthritic knees and to compare these findings with those of age-matched healthy controls.
  
  
  METHODS
  Female subjects above 40 years of age with (N1  = 20) and without osteoarthritis (OA) (N2  = 10) were imaged on a 3 Tesla MR scanner using a custom made loading device. MR images were acquired, with the knee flexed at 20°, with and without a compressive load of 50% of the subject's bodyweight. The subjects were categorized based on the radiographic evidence of OA. Three different zones (outer, middle, and inner) of meniscus body were defined (each occupying 1/3rd the width). After adjusting for age and body mass index in the general linear regression model, repeated measures analysis of variance was used to detect significant differences in T1ρ and T2 with and without loading.
  
  
  RESULTS
  In the unloaded condition, the average T1ρ and T2 times were elevated in the outer and middle zones of the medial meniscus in OA subjects compared with the controls. In the loaded condition, T1ρ and T2 times of the outer zone of the medial meniscus was significantly elevated in OA subjects compared with controls. Finally the change (from unloaded to loaded) was significantly higher in controls than OA subjects (15.1% versus 8.3%; P = 0.039 for ΔT1ρ , and 11.5% versus 6.9%, P = 0.049 for ΔT2 ).
  
  
  CONCLUSIONS
  These findings suggest that while the OA process appears to affect the relaxation times of all regions within the meniscus, it may affect some regions sooner or to a greater degree. Furthermore, the differences in the change in relaxation times between unloaded and loaded conditions may reveal evidence about load transmission failure of the outer zone of the medial meniscus in subjects with knee OA. It is possible that these metrics (ΔT1ρ and ΔT2 ) may be valuable as an early biomechanical biomarker, which could be used to predict load transmission to the underlying articular cartilage.
authors.affiliation: Musculoskeletal and Quantitative Imaging Research Group Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, USA.
authors.forename: Karupppasamy
authors.initials: K
authors.lastname: Subburaj
authors.forename: Richard B
authors.initials: RB
authors.lastname: Souza
authors.forename: Bradley T
authors.initials: BT
authors.lastname: Wyman
authors.forename: Marie-Pierre Hellio
authors.initials: MP
authors.lastname: Le Graverand-Gastineau
authors.forename: Xiaojuan
authors.initials: X
authors.lastname: Li
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Link
authors.forename: Sharmila
authors.initials: S
authors.lastname: Majumdar
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008592:Menisci, Tibial / Q000503:physiopathology*; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000503:physiopathology*; D010865:Pilot Projects; D011446:Prospective Studies; D015203:Reproducibility of Results
keywords: MR relaxation times; T1ρ and T2; acute loading; meniscus; osteoarthritis