My 82-year old mother is doing well but starting to have some back and leg pain. The doctor says it’s caused by spinal stenosis. I notice when she bends forward the pain goes away and when she straightens up, it gets worse again. Can you explain why this is?

Spinal stenosis is a condition in which the spinal canal narrows and compresses the spinal cord and nerves. This usually occurs over time as a natural process of spinal degeneration. It’s not likely to become symptomatic until a person is 60 years old or older.

It can sometimes occur in younger adults if it’s caused by spinal disc herniation, osteoporosis, or a tumor. Spinal stenosis can affect any part of the spine but occurs most often in the lumbar spine. Lumbar spinal stenosis causes low back pain. Patients also report leg pain or discomfort with certain positions.

Bending backwards or even just straightening up for older adults with spinal stenosis decreases the spinal canal space. Anything that does this can put pressure on the nerve tissue and cause pain.

As the vertebral bones extend, the thick ligament inside the spinal canal buckles and pushes forward against the spinal nerve. At the same time, the disc material bulges slightly in a posterior (backward) direction. The effect on the spinal nerve is the same (pressure).

Bending forward or flexing the spine has the opposite effects. The forward movement of the vertebral bones opens up the spinal canal. The ligament stretches tight and the buckling is relieved. This phenomenon is called postural dependency.