Human Spinal Anatomy

If you have back pain its best that you have some understanding of your spinal anatomy. It can be quite confusing to try and understand your back problem unless you know a little about the different parts that make up the human spine.

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Vertebrae - the building blocks of the human spine

Despite the fact that large numbers of people have lower back pain your spine is not weak and vulnerable at all - it is a really strong and flexible structure. It is designed to support your body, protect your spinal cord and allow movement, and it does all these different things really well.

Your back is divided up into sections:

  • Cervical - Neck Area - 7 vertebrae
  • Thoracic - Mid Back - 12 vertebrae
  • Lumbar - Lower back - 5 vertebrae
  • Sacral and Coccyx - tailbone and base of spine - 5 and 4 fused vertebrae respectively
The different areas of the backbone - shown from the back (left) and the side (right)
picture of the human spine from the side and the back
  • The backbone is made up of bony blocks called vertebrae, these are tough, chunky bones.

  • The parts of your spine you can see from behind when you look in the mirror are the bony parts at the back of the vertebrae, these are called the spinous processes.

  • The vertebra also has bony projections to the sides and these are called transverse processes, you can't see these yourself but your physiotherapist or chiropractor can feel them.

  • The vertebrae are separated from one another by big, shock absorbing spinal discs.

  • Each vertebra overlaps the one below at the back to form joints, one on each side.

  • These joints are called facet joints (they are sometimes called zygapophoseal joints too but as that is such a mouthful I think we will stick to facet joints).

Typical Vertebrae and Facet Joints

The vertebral body is a largish, flat area and makes up the bulk of the bone. The spinal disc sits on top of this area and acts as a really efficient cushion between the bones.

Diagram of a Typical Lumbar Vertebra Showing Facet Joints
typical vertebrae diagram showing facet joints

These bony parts together make a ring of bone, a triangular type space in the middle of the bone. That space is called the spinal canal and the spinal cord runs down through this space, nicely protected by bone on all sides.

Each vertebra overlaps the next at the back and these areas of overlap form joints. There are two joints for each vertebra, one on either side and they are called facet joints.

These facet joints allow movement between the vertebra, they are the inks in the chain. without them we would be stiff and unable to move our spines. These joints are the key to understanding many types of back pain.

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Movements in the Lower Back at the Facet joints

I often describe these joints to my patients as very like finger joints, allowing movements in certain directions.

In the lower back the main movements that take place are forward bend, backward bend, and sideways bending. There is not much rotation or twisting in the lower part of the back - that mostly takes place a bit higher up.

The facets joints slide and glide over one another during these movements. If these joints become very stiff or have significant age changes they can become very sore. It is also not at all unusual for one of these joints to become strained and painful.

References

Varlotta, G.P. et al., 2011. The lumbar facet joint: a review of current knowledge: part 1: anatomy, biomechanics, and grading. Skeletal radiology, 40(1), pp.13–23.

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01-Feb-2013


 

 

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