The effects of acute loading on T1rho and T2 relaxation times of tibiofemoral articular cartilage

SummaryObjectiveTo evaluate the effect of acute loading on healthy and osteoarthritic knee cartilage T1ρ and T2 relaxation times.DesignTwenty subjects with radiographic evidence of osteoarthritis (OA) and 10 age-matched controls were enrolled. Magnetic resonance imaging (MRI) acquisition, including T1ρ and T2 map sequences were performed unloaded and loaded at 50% body mass. Cartilage masks were segmented semi-automatically on registered high-resolution spoiled gradient-echo (SPGR) images for each compartment (medial and lateral). Cartilage lesions were identified using a modified Whole Organ Magnetic Resonance Imaging Score (WORMS) score. Statistical differences were explored using separate two-way (group × loading condition) Analysis of Variance (ANOVA) using age as a covariate to evaluate the effects of loading on T1ρ and T2 relaxation times.ResultsA significant decrease in T1ρ (44.5 ± 3.8 vs 40.2 ± 4.8 ms for unloaded and loaded, respectively; P < 0.001) and T2 (31.8 ± 3.8 vs 30.5 ± 4.8 ms for unloaded and loaded, respectively; P < 0.001) relaxation times was observed in the medial compartment with loading while no differences were observed in the lateral compartment. This behavior occurred independent of WORMS score. Cartilage compartments with small focal lesions experienced greater T1ρ change scores with loading when compared to cartilage without lesions or cartilage with larger defects (P = 0.05).ConclusionsAcute loading resulted in a significant decrease in T1ρ and T2 relaxation times of the medial compartment, with greater change scores observed in cartilage regions with small focal lesions. These data suggest that changes of T1ρ values with loading may be related to cartilage biomechanical properties (i.e., tissue elasticity) and may be a valuable tool for the scientist and clinician at identifying early cartilage disease.