This post will explain why and how we can get leg pain from our lower back with some informative videos that help us understand.
To start with lets quickly cover the different types of pain;
- Nociceptive -> pain provoked by noxious stimuli e.g. touching a hot plate, being pinched or exposure to a chemical.
- Neuropathic -> damage or irritation to our nerves or nervous system
- Nociplastic -> pain arising from the altered function of our nervous system (Jones and Rivett 2018)
Now that we have covered the main types of pain, let’s explore how and why we get referred pain.
Referred pain can be a result of neuropathic and nociceptive pain.
Somatic referred leg pain
- Somatic referred pain is pain that is being referred into your leg from a structure in your back.
- Somatic structures include: muscles, discs, ligaments, bones etc. Anything musculoskeletal tissue that has a nerve supply is classed as a somatic structure.
- Referred pain is pain perceived at a location other than the site of the painful stimulus/origin. It is the result of a network of interconnecting sensory nerves that supplies many different tissues. When there is an injury at one site in the network it is possible that when the signal is interpreted in the brain signals are experienced in the surrounding nervous tissue. Source: https://www.physio-pedia.com/Referred_Pain
A common low back example is an inflamed lumbar facet joint referring to pain into your buttock and back of thigh area.
Radicular referred leg pain
- Although commonly referred to as ‘sciatica’, the term lumbar radicular pain (LRP) is anatomically more correct. This is because it can affect other nerves, not just the sciatic nerve.
- The pain may track down into different areas of your thigh, lower leg and foot, either the front, back or side.
- This is when a nerve is irritated or compressed as it’s coming out of your spinal cord and passing through the radicular canal between your vertebrae. The radicular canal is pictured below.
- Radicular pain will be felt where that spinal nerve travels to and the area it supplies. Each lumbar spinal nerve supplies a different area of your leg, in what we call a dermatome distribution. See the image below:
Image Source: https://www.healthline.com/health/dermatome
Radiculopathy occurs when a compressed or inflamed nerve root results in neurological deficits, such as problems with reflexes, numbness, and/or weakness. Radicular pain and radiculopathy often occur together, but can be independent.
Radicular syndrome is often caused by direct pressure from a herniated disc or degenerative changes in the spine that cause irritation and inflammation of the nerve roots by bone spurs or collapse of the nerve root tunnels (foramen).
Sensory symptoms are more common than motor symptoms, and muscle weakness is usually a sign that the nerve compression is more severe. The quality and type of pain resulting from radicular syndrome can vary, from dull, aching and difficult to localize, to sharp and burning.
Causes of radicular pain
- Disc herniation (most common)
- Spinal stenosis
- Synovial cysts
- Infection
- Infestation
- Tumour
- Vascular abnormalities
Distinguishing features of lumbar radicular pain and somatic referred pain
| Feature | Radicular pain | Somatic referred pain |
|---|---|---|
| Distribution | Entire length of lower limb BUT below knee > above knee | Anywhere in lower limb BUT proximal > distal |
| Pattern | Narrow band Travelling Quasi segmental but not dermatomal Not distinguishable by segment | Wide area Relatively fixed in location Quasi segmental but not dermatomal Not distinguishable by segment Boundaries difficult to define |
| Quality | Shooting, lancinating, like an electric shock | Dull, aching, like an expanding pressure |
| Depth | Deep as well as superficial | Deep only, lacks any cutaneous quality |
Source: https://www.racgp.org.au/afpbackissues/2004/200406/20040601govind.pdf
Summary
There can be many different causes and reasons why we experience leg pain. That is why it is important to be assessed by a trained physiotherapist, so that the specific causes can be identified and addressed. This will often involve manual therapy and a targeted exercises program. Later in this series we will discuss different management options.
Article written by:
Henry Pope, Physiotherapist, myPhysioSA.
