A lot of patients who consult us with lower back pain also experience pain which radiates down one or both of their legs. This is often labelled as ‘sciatica’ or as the consequence of a ‘slipped disc’.
In this series of articles I would like to discuss some of the many common causes of radiating leg pain as well as discussing the truths and myths around the term ‘sciatica’ and ‘slipped disc’.
In this article I will discuss:
- What is radiating pain and why does it occur
- Common patterns of radiating leg pain
- Some of the common causes of radiating leg pain
What is radiating pain and why does it occur?
Radiating pain is the sensation of pain which is felt occurring from the source area of pain and extends to a point further away from the area which is causing the pain.
This process is governed by the rules of centralisation and peripheralisation. Most conditions begin centrally, meaning that they originate in the spine or skull or possibly the hips and shoulders (centralisation). As these conditions progress over time and the tissues of the body become more dysfunctional, irritated and inflamed the symptoms begin to radiate away from the centre down the limbs (arms and legs) towards the extremities (hands and feet) this is known as peripheralisation.
Common patterns of radiating leg pain
The most common pattern of leg pain is from the lower back, into the buttock and progressing down the back of the leg, potentially all the way towards the heel and bottom of the foot. This is often incorrectly labelled as ‘Sciatica’ for reasons I will discuss in the next article.
Other common patterns of radiating leg pain include pain down the outside of the thigh crossing over the front of the shin and into the top of the foot.
Referral into the groin and the front of the thigh is another common pattern which is seen.
Common causes of radiating leg pain
In general radiating leg pain is usually caused by 4 primary categories. In reality most biomechanical cases are made up of a mixture of several of the categories.
- Nerve Root irritation– Nerves can become irritated for various reasons however the most common reason is due to chemical irritation and inflammation due to dysfunction of the joints and muscles of the lower back.
- Joint Dysfunction– As well as being involved in chemical irritation and inflammation of the nerve roots the joints of the lower back themselves can also radiate pain down into the thighs and groin.
- Myofascial pain– This is when a muscle becomes dysfunctional and generates ‘knots’ or ‘Myofascial Trigger Points’. There are several muscles throughout the lower back, buttocks and leg which when aggravated will send pain down the leg.
- Discogenic Pain– The discs in the lower back, when damaged can cause radiating leg pain through several mechanisms. They can commonly cause nerve root irritation, similarly to a joint, which aggravates the nerve and causes pain. Less commonly the disc can herniate and physically compress the nerve resulting in pain as well as neurological changes. Discogenic pain is again, like ‘sciatica’, often incorrectly labelled as a ‘slipped disc’. The correct use of the term ‘sciatica’ and ‘slipped disc’ will be discussed in future articles.
Hopefully this article has begun to shed some light on the multi-faceted condition that is referred leg pain. As the series continues we will cover the common causes in more depth, including how they may be diagnosed and treated.
Andre Smy (chiropractor)