The 3D shape of the intervertebral disc (IVD) is modeled in this work from a population of samples. Heretofore, 3D models of the disc have been created from individual samples only. L3/L4 discs were segmented from 14 magnetic resonance images. The mean shape was calculated using a signed distance function representation, and principal components analysis was used to re-express the residual variability with an orthonormal basis. The first basis vector, which represents lateral bulging of the disc, expresses the majority of the population's shape variation. This vector was also significantly correlated with Pfirrmann grade (p<0.01), a measure of disc degeneration. The IVD shape model can thus be used to generate an average IVD shape for the population, as well as shapes for specific degenerative grades.