Spinal anatomy is a remarkably intricate structure of strong bones, flexible ligaments and tendons, extensive muscles and highly sensitive nerves and nerve roots. Without question, the composition and function of the spine is a marvel of nature, providing us with a unique combination of:
- Structure to allow us to stand upright and move with precision
- Protection for the spinal cord and nerve roots to safely relay messages to and from the brain and the rest of the body
- Shock absorption accepts jolts and stress as we move about
- Flexibility, especially in the lower and upper spine, allowing us to bend and twist in a full variety of movements
- Strength provided by the bones, discs, joints and supportive muscles and connective tissue
Once back pain starts, however, the many benefits of this intricate anatomical construct can quickly be lost. Here are the basics of anatomical causes of spine pain:
The cervical spine (neck) supports the weight of your head and protects the nerves that come from your brain to the rest of the body. This section of the spine has seven vertebral bodies (bones) that get smaller – and provide more rotation - as they get closer to the base of the skull.
Most episodes of acute neck pain are due to a muscle, ligament or tendon strain, which is usually caused by a sudden force (e.g. whiplash) or from straining the neck (e.g. sleeping in the wrong position).
If you have neck pain that lasts longer than two weeks to three months, or with predominant arm pain, numbness or tingling, there is often a specific anatomic abnormality causing the symptoms, such as a herniated disc, spinal stenosis, etc.
Upper back pain
The 12 vertebral bodies in the upper back that are attached to the rib cage make up the thoracic spine (middle or upper back) are firmly attached to the rib cage at each level, providing a great deal of stability and structural support, protecting the heart, lungs and other important organs within the chest.
Because there is little motion in the upper spine, it is rare to have pain caused by a herniated or degenerated thoracic disc. More common causes of upper back pain include irritation of the large back muscles and shoulder or joint dysfunction.
Lower back pain
Because the lower back carries the most load with the least structural support, it is the most likely to wear down or suffer injury.
Most episodes of lower back pain are caused by muscle strain. Even though this doesn't sound like a serious injury, the pain can be severe. Strong abdominal muscles and back muscles are important to provide support for this area of the spine and avoid injury.
Motion in the lower back is divided between the five motion segments, with a disproportionate amount of the motion in the lower segments (L4-L5 and L5-S1) - the two segments most likely to be a source of pain from conditions such as degenerative disc disease or a herniated disc. Frequently, a lower back problem can cause sciatica, or pain that radiates down the sciatic nerve into the leg.
Pain at the bottom of the spine
The iliac bones are part of the pelvis, and the sacrum is connected to this part of the pelvis by the sacroiliac joints. Pain can occur in the sacroiliac joints (where the sacrum connects to the pelvis), called sacroiliac joint dysfunction, and in the coccyx (tailbone), called coccydynia. Both of these conditions are more common in women than men.
The spine is an anatomically complicated structure. Knowing the basics can help you have a more meaningful discussion with your spine care provider.