Understanding Back Pain: Your Spine and How it Works
The spine consists of 24 freely moveable vertebrae which articulate at the bottom with the sacrum and at the top with the occiput, which is the base of the skull. Each vertebra is separated from the next by a disc, which is a shock absorbing cushion that provides the surface for each vertebra to move upon the next; hence they are “freely movable” upon one another. When we consider how two vertebrae move in relation to one another, we refer to movement of a joint. Thus, a spinal joint consists of two bones and the disc in between them. There are specific normal ranges of movement for these joints which often become compromised or dysfunctional long before the onset of pain. Insidious back pain is most commonly the result of long standing spinal joint dysfunction which goes undetected and unmanaged until the pain actually presents.
The spine is classified into three regions and the individual vertebrae are identified numerically within each region. The cervical region refers to the neck and consists of seven vertebrae positioned so that they form what is called a lordosis. Lordosis is the description of how the vertebrae align themselves into a c-shaped curvature when you look on a lateral (side-view) x-ray. For example, the third vertebra in the cervical region is identified as “C3”
Below the cervical region, the next twelve vertebrae comprise the thoracic region. Each thoracic vertebra articulates with a rib on both sides and the alignment in this region forms a kyphosis, or backwards c-shaped curvature. Similarly, the fifth vertebra here is referred to as “T5”, or thoracic vertebra number five.
The final 5 vertebra make up what is considered the lumbar region; the lower back, which like the cervical region is aligned as a lordosis. “L5”, the fifth and final vertebra of the lumbar spine articulates with the sacrum, which is the large triangular shaped bone at the base of the back. This joint is also separated by a disc and is what we refer to as the lumbosacral joint. Dysfunction in this joint is the most common source of debilitating lower back pain, as by natural design it is anatomically vulnerable to injury. Finally, the sacrum articulates with the ilium, the large pelvic bone on either side of the sacrum, forming the right and left sacroiliac joints. These joints are important weightbearing joints for the pelvis and they move back and forth with walking and running. Ultimately, the sacrum meets with the coccyx at its base and forms the last spinal joint, the sacrococcygeal joint.
Based upon this detailed anatomical design, we can see how the body works like a machine. There is an optimal degree of function obtained when structures are aligned properly and a less optimal degree of function when changes occur, leading to spinal joint dysfunction and pain. The best and most simple analogy is to think about driving a car without rotating the tires. The car will continue to move when the tires are unbalanced, but eventually one tire will wear out because of the prolonged stress placed upon it. So it is with back pain and functional pathology.
The first step in understanding back pain and how to manage it is to understand how the spine works. This overview of the spine explains the general concepts of normal spinal structure and function and introduces the concept that changes from the normal structure affect spinal function and contribute to dysfunction, deconditioning and degradation of a joint over time. This process predisposes to injury and ultimately results in pain. At the time that pain presents, there has often been long standing dysfunction which has caused irreversible damage to the spine itself. Therefore, addressing the dysfunction before the pain presents is an important tool in spinal health.
In part two, we will look at how the soft tissues (muscles, ligaments) that attach to the spine contribute to back pain.
