Patient was treated as a random effect, and disk and presence of an annular tear on initial MR imaging were treated as fixed effects on all the analyses. Initial signal-intensity and degeneration grades were used as the dependent variables to analyze patterns at baseline. Signal-intensity grade and degeneration grade for both stages (initial, follow-up) were the dependent variables, and stage was added as a fixed effect, to analyze change, as was the time between studies, to control for differences between patients.