Back structures The lumbar (or<unk> er back) region is made up of five vertebrae (L1–L5), sometimes including the sacrum. In between these vertebrae are fibrocartilaginous discs, which act as cushions, preventing the vertebrae from rubbing together while at the same time protecting the spinal cord. Nerves come from and go to the spinal cord through specific openings between the vertebrae, providing the skin with sensations and sending messages to muscles. Stability of the spine is provided by the ligaments and muscles of the back and abdomen. Small joints called facet joints limit and direct the motion of the spine. The multifidus muscles run up and down along the back of the spine, and are important for keeping the spine straight and stable during many common movements such as sitting, walking and lifting. A problem with these muscles is often found in someone with chronic<unk> , because the back pain causes the person to use the back muscles improperly in trying to avoid the pain. The problem with the multifidus muscles continues even after the pain goes away, and is probably an important reason why the pain comes back. Teaching people with chronic<unk>  how to use these muscles is recommended as part of a recovery program. An intervertebral disc has a gelatinous core surrounded by a fibrous ring. When in its normal, uninjured state, most of the disc is not served by either the circulatory or nervous systems – blood and nerves only run to the outside of the disc. Specialized cells that can survive without direct blood supply are in the inside of the disc. Over time, the discs lose flexibility and the ability to absorb physical forces. This decreased ability to handle physical forces increases stresses on other parts of the spine, causing the ligaments of the spine to thicken and bony growths to develop on the vertebrae. As a result, there is less space through which the spinal cord and nerve roots may pass. When a disc degenerates as a result of injury or disease, the makeup of a disc changes: blood vessels and nerves may grow into its interior and/or herniated disc material can push directly on a nerve root. Any of these changes may result in back pain. Pain sensation Pain is generally an unpleasant feeling in response to an event that either damages or can potentially damage the body's tissues. There are four main steps in the process of feeling pain: transduction, transmission, perception, and modulation. The nerve cells that detect pain have cell bodies located in the dorsal root ganglia and fibers that transmit these signals to the spinal cord. The process of pain sensation starts when the pain-causing event triggers the endings of appropriate sensory nerve cells. This type of cell converts the event into an electrical signal by transduction. Several different types of nerve fibers carry out the transmission of the electrical signal from the transducing cell to the posterior horn of spinal cord, from there to the brain stem, and then from the brain stem to the various parts of the brain such as the thalamus and the limbic system. In the brain, the pain signals are processed and given context in the process of pain perception. Through modulation, the brain can modify the sending of further nerve impulses by decreasing or increasing the release of neurotransmitters. Parts of the pain sensation and processing system may not function properly; creating the feeling of pain when no outside cause exists, signaling too much pain from a particular cause, or signaling pain from a normally non-painful event. Additionally, the pain modulation mechanisms may not function properly. These phenomena are involved in chronic pain.
Low back pain
Pelvic fracture
Back pain
Pelvic girdle pain
Middle back pain
Radicular pain
Pelvic pain
Xiphodynia