All MR images, taken at 5 lumbar intervertebral disc levels from the first lumbar (L1) vertebra to the first sacral vertebra (S1), were independently evaluated by 2 experienced orthopedic specialists in a random order using a grading system for LDD assessment. Using a comprehensive grading system for LDD, discs were classified into 5 grades, as described by Pfirrman et al. This system uses characteristics of disc structure, distinction between the nucleus and annulus, MRI signal intensity, and intervertebral disc height for grading, and has been accepted as a standardized and reliable evaluation tool for assessment of MRI disc morphology. The assessment was blinded so as not to disclose any knowledge about the athlete's condition, such as the subjective functional disability level of LBP. When the 2 experienced orthopedic specialists had differing opinions on disc grades, the disagreements were debated and resolved with discussion.