4 Part series on Low Back Pain

Part 2 – Where does pain in the back come from?

part one of this series (see previous blog post) looked into the shocking statistics that demonstrate the significant problems back pain is causing to australians. it effects so many of us. in this blog post, we look more closely into where the pain actually comes from. 


Back pain can be acute or chronic, sharp or achey, radiate to your legs or hang in the lower back and buttock. But where does the pain actually come from?

Back pain is commonly due to general wear and tear of all the structures around your back. This can include the joints, the disc, and the muscles. Typically, not just one structure is involved, but a bunch of them.  

Most commonly, however, the disc is the main source of pain (does a ‘slipped disc’ sound familiar?). There are 5 lumbar vertebrae. In between the vertebrae there are discs, which act as cushions between the vertebrae. The discs have an:

  • inner part, called the nucleus pulposus which is like soft jelly
  • outer part, called the annulus fibrosis which is like a harder jelly


Left: Demonstrates your entire spine with your cervical (neck), thoracic (mid back) and lumbar (lower back) vertebrae.
Right: Shows how the disc and vertebrate are positioned. 

When the disc herniates, part of the nucleus leaks backwards. From more minor back injury to more severe this is what happens to the disc:

  • The nucleus can just touch the edge of the disc, causing pain (protrusion)
  • the nucleus touches the edge of the disc and if the wall weakens, this can irritate the nerve roots (herniation)
  • a portion of the disc leaks out through a tear in the disc’s outer wall (extrusion) and may separate from the disc itself (worst case scenario, sequestration). 

The picture below summarises this. 

Below is what a bulging disc typically looks like on MRI (side on view). 

The disc doesn’t necessarily have to herniate to cause pain. It can degenerate or thin. In a normal disc, its height is maintained by water and protein. As we age or as the disc degenerates, the water and protein content in the disc, decreases. See below. 




Sciatica describes the symptoms of leg pain and possibly tingling, numbness or weakness that originates in the lower back and travels through the buttock and down the large sciatic nerve in the back of the leg. Most commonly, sciatica is caused by a protruding disc, degenerated disc or a narrowing of the boney canal that the nerve passes through. 

The majority of us, however, do not have 1 particular structure that is the main source of our back pain. We typically have general wear and tear that affects many structures in our back. Therefore we present to a health professional with a grumbly back that never seems to get better. Keep reading the next 2 posts, where we will cover:

  • Part 3 – causes and symptoms
  • Part 4 – treatment 



About Physiotonic

Physiotonic are expert Sports Physiotherapists who run group exercise classes. We focus specifically on buttock muscle strengthening, deep core activation and flexibility. This will help you improve your posture. We specialise in helping runners to improve their running technique and running efficiency. The Physiotonic blog has posts on all sorts of health and fitness tips to help get you on your way!

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