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By Dr. David Borenstein M.D. Medically Reviewed by Dr. C.H. Weaver M.D. 7/2022

After more than twenty years of caring for people with back pain, I’ve learned that taking the time to explain the anatomy and biomechanics of the lumbar spine goes a long way in helping people understand their situation and alleviate anxiety and fear.

Because most people have no idea of what caused their back injury in the first place, they often experience the same injuries again and again. On the other hand, I’ve seen people become so afraid of bringing on more pain, even with normal body motion, that they become stiff—like statues. They do not realize that their rigid posture does not protect them from pain, but perpetuates it.

People who don’t understand the cause of their pain often do not understand the prescribed treatments, and they don’t follow through with self-care, including the specific exercises they are told to perform daily. So, understanding how your back works will help you get rid of pain.

The Lumbar Discs and Bony Joints

The lumbar spine is a beautifully engineered structure with two primary functions: movement and protection of the spinal cord. It is made up of bone, discs, ligaments, muscles, nerves, and blood vessels. The spine contains thirty-three vertebrae, each lined up one atop another and divided into five areas: cervical (neck), thoracic (chest), lumbar (low back), sacral (pelvis), and coccygeal (tail bone).

  • Cervical vertebrae facilitate motion in all directions.
  • Thoracic vertebrae support the ribs and allow rotation of the body.
  • Lumbar vertebrae support the upper part of the body and allow forward and backward motion.

When we look at the spine from the side, balanced so your head is we can see that it is not straight, but curved. directly over the center of The neck and low back have forward-facing gravity in your pelvis. Notice curves, while the chest and sacral spine have the balance between the forward curves (lordosis) of the backward-facing curves. These curves neck and low back and the allow room for the heart and lungs in the backward curves(kyphosis) of chest, while keeping the head centered over the chest and pelvis. lower body and the pelvis. This position is well balanced and strong.

Because each section of the spine serves a different function and motion, the vertebrae in each portion of the spine have specific shapes. The lumbar spine contains five vertebrae numbered one through five. You may hear a doctor refer to one of your vertebrae as L-4, for example. This refers to the fourth lumbar vertebra. The assigned letters correspond to the section of the spine.

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Facet Joints. Joints are formed where vertebrae meet at top and bottom. Each vertebra has four facet joints, two formed with each vertebra directly above and below, right and left. The vertical orientation allows for bending forward, the greatest degree of motion, and backward, a lesser degree of motion. The structure and orientation of the lumbar facet joints limit the twisting motions of the lumbar spine. The greatest rotation of your spine occurs in the chest, the thoracic portion. The facet joints have cartilage on their surfaces, lining tissue (synovium) that makes joint fluid, and a joint covering, a capsule that keeps the joint fluid in and the bones together.

The “His and Hers” Sacroiliac. The sacrum is a large triangular bone formed by five fused vertebrae wedged between the pelvic bones. The top of the sacrum is the first sacral vertebra, or S-1. The sacroiliac joints are formed between the sacrum and the iliac bones. In this part of the spine, we can see male and female anatomical differences. In men, more of the sacrum is attached to the ilium, and in women, the sacroiliac joints widen during childbirth. These differences also play a role in the typical gait we associate with men and women. In men, the hip structure tends to be stable during normal walking movements; in women there is a natural sway of the hips. The sacrum contains the end of the spinal canal and, therefore, nerves.

The Coccyx. The tail bone, as the coccyx is also known, consists of four tiny fused vertebrae located between the cheeks of the buttocks. This is well padded, which makes it difficult to fracture.

From Back in Control by Dr. David Borenstein