The spine is made up of bone segments called vertebrae. Vertebrae have two parts: 1) the cylinder-shaped vertebral bodies to the front; and 2) the boney bridges making up the facet joints at the back. Most of the spine is flexible enough to let people bend, stretch, and lift. Between the bones of the spine are small discs that are hard on the outside and soft and jelly-like on the inside. The spinal bones are connected by the facet joints at the back and by the discs at the front.
The nerves of the spinal cord run through the spinal canal, which is just behind the vertebral bodies, and separate into roots along the length of the spinal cord and at the tail end of the spine. Some of them pass through the pelvis to become the sciatic nerves, which pass down each leg. Problems with the vertebrae, joints, or discs can all cause back disorders. Back disorders can cause mild to very severe backache.
Many Canadians between the ages of 20 to 65 will develop back pain. Though it hurts, back pain is rarely caused by a serious disease and usually disappears on its own. It often comes back, however, making it one of the most common reason people see doctors.