Muscle asymmetry and fatty infiltration resulting from lumbosarcal nerve root compression are associated with movement ability directly. However, the specific rule remains unclear. In this study, we used three dimensional fast imaging empolying steady-state acquisition with phase cycling(3D-FIESTA-C) and iterative decomposition of water and fat with echo asymmetry and least-squares estimation intelligent quantification (IDEAL-IQ) technique to evaluate the changes quantitatively. We found muscle changes were side- and level-specific, affected by several other factors. Muscle content is suggested as a good parameter for clinical evaluation.