Acquired stenosis is a degenerative condition. Patients generally become symptomatic in their 50s or older. Degenerative changes of the spine can include osteophyte formation, facet hypertrophy, bulging disks, and hypertrophy of the ligamentum flavum. Any of these processes can result in canal or foraminal narrowing. Degenerative spondylolisthesis can further compromise the canal.
Osteophytes can form anteriorly or posteriorly.
Posterior osteophytes narrow the intraspinal diameter and cause lateral recess stenosis as well. This results in spinal cord or nerve root impingement. Furthermore, arthritic degeneration causes the formation of synovial cysts and hypertrophy of the facet joints which further compromises the patency of the spinal canal and the neural foramina. During aging, the disks dehydrate, and can compress, and bulge. This can cause tilting, slippage, or rotation of vertebral bodies.