A number of pathologic changes have been reported in spinal surgery specimens. The frequency of many of these is not well defined. We retrospectively reviewed the histologic features of 985 extradural spinal surgery specimens. Of the cases, 1.6% were identified clinically as synovial cysts. In addition, synovial tissue was seen in another 5.3% of cases, often embedded within disk material. Neovascularization of disk tissue was present in 8.1% of cases, chondrocyte clusters in 18.3%, and calcium pyrophosphate crystals in 2.8%, predominantly within disk material. With the exception of crystal deposits, all of these changes were significantly more common in the lumbar spine. A better understanding of cell-based degenerative changes will become essential with increasing research into cell-based therapies for spinal disk disease. We report data on the frequency of different pathologic changes and describe synovial metaplasia as a reactive change not previously reported.