Low back pain

[Mark Zuckerberg]

Low back pain and neck pain are among the most common reasons for health care visits. The pain usually results from problems with the musculoskeletal system—most notably the spine, including the bones of the spine (back bones, or vertebrae), disks, and the muscles and ligaments that support it. Occasionally, low back pain results from a disorder that does not involve the musculoskeletal system.
Low back pain becomes more common as people age, affecting more than half of people over 60. It is very costly in terms of health care payments, disability payments, and missed work.
The spine (spinal column) consists of back bones (vertebrae). There are shock-absorbing disks between each of the vertebrae. The disks have a tough, outer layer of fibrocartilage and a soft, jelly-like interior called the nucleus. Each of the vertebrae have two joints behind the disks. The joints are called facet joints. The facets of one vertebral body rest on the facets of the one below it, forming a joint. The facet joints and thus the spine are stabilized by ligaments and muscles, which include the following:

Two iliopsoas muscles, which run along both sides of the spine
Two erector spinae muscles, which run along the length of the spine behind it
Many short paraspinal muscles, which run between the vertebrae

The abdominal muscles, which run from the bottom of the rib cage to the pelvis, also help stabilize the spine by supporting the abdominal contents. The muscles in the buttocks also help stabilize the spine. All together, these muscles are referred to as the core muscles.
Enclosed in the spine is the spinal cord. Along the length of the spinal cord, the spinal nerves emerge from the sides through spaces between the vertebrae to connect with nerves throughout the body. The part of the spinal nerve nearest the spinal cord is called the spinal nerve root. Because of their position, spinal nerve roots can be squeezed (compressed) when the spine is injured, resulting in pain.
The lower spine (lumbar spine) connects to the spine in the upper back (thoracic spine) above and to the pelvis through the (sacrum. The lumbar spine is flexible to allow turning, twisting and bending, and provides strength—for standing, walking, and lifting. Thus, the lower back is involved in almost all activities of daily living. Low back pain can limit many activities and reduce the quality of life.