Changes in MR relaxation times of the meniscus with acute loading: an in vivo pilot study in knee osteoarthritis.

PurposeTo prospectively evaluate changes in T-1 and T-2 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. Materials and MethodsFemale subjects above 40 years of age with (N-1=20) and without osteoarthritis (OA) (N-2=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 degrees, 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 T-1 and T-2 with and without loading. ResultsIn the unloaded condition, the average T-1 and T-2 times were elevated in the outer and middle zones of the medial meniscus in OA subjects compared with the controls. In the loaded condition, T-1 and T-2 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 T-1, and 11.5% versus 6.9%, P=0.049 for T-2). ConclusionThese 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 (T-1 and T-2) may be valuable as an early biomechanical biomarker, which could be used to predict load transmission to the underlying articular cartilage.J. Magn. Reson. Imaging 2013. (c) 2013 Wiley Periodicals, Inc. J. Magn. Reson. Imaging 2015;41:536-543.(c) 2013 Wiley Periodicals, Inc.