Spondylosis, or spinal arthritis, can affect any component of your spine. To understand how and why, it's helpful to understand the general anatomy of the spine.

Your spine is divided into regions: There's your neck (cervical spine), mid-back (thoracic spine), and low back (lumbar spine). At the lower end of your spine, you also have the sacrum and the coccyx, which is commonly called your tailbone. Spondylosis occurs in all regions of your spine.

The bones in your spine are called your vertebrae, and you have 33 of them in your spinal column.

• Cervical spine: The vertebrae in your neck are labeled C1-C7, meaning that you have 7 vertebrae in that region.
• Thoracic spine: Most adults have 12 vertebrae in the thoracic spine (T1-T12), which goes from your shoulders to your waist.
• Lumbar spine: There are 5 vertebrae in your low back (L1-L5).
• Sacrum/coccyx: Your sacrum is made up of 5 vertebrae between the hipbones that are fused into one bone. The coccyx is small fused bones at the very tail of your spine (hence the tailbone).

In between your vertebrae, you have intervertebral discs. These act like pads or shock absorbers for your spine as it moves. Each disc is made up of a tire-like outer band called the annulus fibrosus and a gel-like inner substance called the nucleus pulposus. The process of aging changes the discs and makes them less able to cushion your movements. As you get older, your intervertebral discs also become more prone to problems; they may bulge or herniate.

Together, the vertebrae and the discs provide a protective tunnel (the spinal canal) to house the spinal cord and spinal nerves. These nerves run down the center of the vertebrae and exit to various parts of the body, where they help you feel and move. You can see the spinal cord running through the vertebrae in the image.

Your spine also has facet joints, which are on the posterior side (back) of your vertebrae. These joints (like all joints in your body) help facilitate movement and are very important to your flexibility. Spondylosis that affects the joints is called osteoarthritis, which is the most common form of arthritis in America.

Your spinal joints are covered by cartilage, which protects your bones as you move. Without cartilage, your bones would rub together—very painful. Unfortunately, your cartilage can be affected by general wear and tear on your spine, and it can wear away. That's when bone spurs (osteophytes) can form as your body attempts to repair itself. (You'll learn more about that in the Causes of Spondylosis.)

Your back also has muscles, ligaments, tendons, and blood vessels. Muscles are strands of tissues that power your movement. Ligaments are the strong, flexible bands of fibrous tissue that link the bones together, and tendons connect muscles to bones. Blood vessels provide nourishment. These parts all work together to help you move.