Lower Back in 5: Sciatic nerve and lumbar nerve roots

Saddle numbness, leg weakness, bladder change The lower back, or lumbar spine, consists of five large vertebrae that support most of the body's weight while allowing bending, twisting, and lifting. Because it sits at the junction between the mobile spine above and the relatively fixed pelvis below, the region absorbs substantial mechanical stress during everyday movement.

Low back pain is one of the leading causes of disability and missed work globally, with the World Health Organization identifying it as a top contributor to years lived with disability. The large majority of cases are classified as non-specific, meaning no single structural abnormality fully explains the pain, and most episodes improve within weeks with continued activity.

A minority of cases involve identifiable causes such as disc herniation, spinal stenosis, or spondylolisthesis, and a very small proportion present with red-flag features suggesting infection, fracture, or cauda equina syndrome that require urgent medical attention. This page covers the region's anatomy, common conditions, assessment approaches, and general rehabilitation patterns.