The focus of this work is to assess the long-term progression of degeneration in the ovine lumbar spine following a minimally invasive model injury comparable to the damage of an intervertebral disc (IVD) herniation. A partial nucleotomy was performed on 18 sheep via the percutaneous dorsolateral approach. The animals were culled at 6 and 12 months to evaluate the damaged and neighboring functional spine units (FSUs) for degenerative characteristics via μ-CT and histology. Both quantitative μ-CT and histology investigations demonstrated statistically significant differences between the native and damaged FSUs investigated. Qualitative analysis of μ-CT revealed numerous pathological markers consistent with intervertebral disc degeneration (IDD), with differences in frequency and severity between the native and damaged FSUs. The annulus fibrosus reforms a pressure seal within 6 weeks, but the extent of the trauma is significant enough to initiate IVD degeneration, which is already clearly visible at 6 months and especially so 12 months post-op. IDD pathology consistent with signs of a herniation was seen in both the 6- and 12-month groups. This technique provides a useful model injury for the preclinical evaluation of IDD in large animal models, especially in regards to simulating disc herniation as well as for testing the efficacy of associated therapies in the future. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2376-2388, 2019.