Spinal stenosis.

Illustration of spinal stenosis in L4 and L5. Spinal stenosis is a pathology located in the lumbar spinal column where the cauda equina nerves pass. It is caused by an intrinsically narrow vertebral canal or a degenerative narrow canal related to a herniated disc, an increase in the volume of rear joints and ligaments that join the vertebrae together, or an instability in the vertebrae with vertebral displacement (or degenerative spondylolisthesis), which decreases the diameter of the canal, compressing the nerves, causing lumbar pain in the lower limbs. (Photo by: Jacopin/BSIP/Universal Images Group via Getty Images)