The back is made up of bones, muscles and other tissues to form the body's trunk, from the neck to the pelvis. The spinal column is the centerpiece. It supports the upper body's weight and houses the spinal cord, which carries the signals that control movement and convey sensations. The spinal column is made up of more than 30 bones, called vertebrae, stacked on top of one another. Each contains a round hole that creates a channel. Small nerves, called roots, enter and emerge from the spinal cord through spaces between the vertebrae. The spaces are protected by round, spongy pads of cartilage called intervertebral discs; these enable some flexibility in the lower back and serve as shock absorbers to cushion the bones as the body moves. The entire network is held in place by bands of tissue called ligaments and tendons.
So what happens when we experience lower back pain? As we age, our bone strength and muscle elasticity decreases, and the intervertebral discs begin to lose fluid and hence their cushioning ability. So we become less flexible. A weakened disc can rupture or bulge outward if the spine becomes overly strained or compressed. This is called a herniated disc. The compression causes the cartilage to push into the space containing the spinal cord or one of the more than 50 nerve roots, causing pain.
Sometimes a herniated disc pressed down on the sciatic nerve, which runs down the spinal column to the pelvis, carrying nerve fivers to the leg. This causes burning lower back pain along with pain through the buttocks, down the leg to below the knee. If the nerve is severely pinched, it can result in numbness or loss of motor control in the leg.