The in vivo effects of unloading and compression on T1-Gd (dGEMRIC) relaxation times in healthy articular knee cartilage at 3.0 Tesla.

Abstract

The purpose was to investigate the in vivo effects of unloading and compression on T1-Gd relaxation times in healthy articular knee cartilage. Ten volunteers were enrolled, and dGEMRIC images of their right knee joints were obtained using 3.0-T MR at three timepoints: directly following exercise ("baseline"), approximately 15 min after unloading ("unloading") and during application of a compressive force (50% of the body weight) generated by a loading device via a footplate ("compression"). Our analysis of variance of pooled data from all cartilage zones demonstrated a significant mean T1-Gd decrease of 56.6 ms between baseline and compression (p < 0.001), and a significant mean decrease of 42.1 ms between unloading and compression (p < 0.001). No significant difference was found between baseline and unloading. Higher mean T1-Gd values were observed in the cartilage contact zone (central femoral and tibial zones; 698.3 +/- 162.2 ms) than in the non-contact zone (anterior and posterior femoral and tibial zones, and dorsal femoral zone; 662.9 +/- 149.3 ms; p < 0.01). T1-Gd times appear to be sensitive to mechanical cartilage stress, and thus, further studies are warranted that investigate the relationship between the biochemical load response and the biomechanical properties of articular cartilage.