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Leg pain associated with low back pain

Low back pain (LBP) can commonly be associated with leg pain-itis sometimes called sciatica.  There are a number of different causes of leg pain so it is important to get an accurate diagnosis as it can be a predictor of chronicity (Selim et al.).  Your physiotherapist can assist with this and ensure the appropriate management is offered.  Many people assume that leg pain means there is compression of a nerve in their low back, however this is only one of many causes.  Imaging such as x-ray, CT or MRI may be suggested, but it is not always needed and sometimes may be detrimental. 

The causes of leg pain associated with LBP include:

Compression

Sometimes nerves can be “squashed” by a physical structure.  There are 2 possible places that compression may lead to leg pain and these include the side opening (lateral foramen) and the central canal.

If your nerves are compressed in the side opening (lateral foramen) you may have leg pain or changes in sensation like pins and needles or numbness right down to the foot.  This may be associated with muscle weakness and reduced reflexes.  If you have these symptoms, it is important that your healthcare professional performs an assessment on your nerve function.  A common reason for compression of the nerves in this area is a disc prolapse.  Recent evidence (elBarzouhiet al.)  has demonstrated that the natural history for disc prolapses is VERY GOOD, studies have shown that over 80% demonstrate a reduction in herniation at a 1 year follow up.   Only people with worsening muscle weakness, reduced reflexes and numbness need to consider surgery.  If a nerve is compressed in this area it can be very painful so it is really important there is effective pain management — your general practitioner or sports physician is the best person to talk to about this.  There may be exercises or postural advice that your physiotherapist can help you with to manage your pain and maintain strength whilst the leg pain is at its most intense.

If your nerves are compressed in the central canal there are different signs.  If it is caused by an acute event (such as a disc prolapse) you may experience sudden and progressive pain, numbness and weakness in your legs along with altered sensation in your buttocks and inner thigh (sometimes called the saddle area). This may be associated with a sudden change in bladder or bowel function such as trouble eliminating urine or waste (retention/constipation) or trouble holding onto it (incontinence).  This problem may require a surgical opinion and is best seen fairly quickly, so seeing your healthcare professional to aid with diagnosis is important.

Sometimes nerves are compressed in the central canal by a slower ageing process such as thickening of ligaments or bony out growths. This will not present with severe, acute leg pain but over time you may notice increasing leg pain and possibly weakness which is worse with standing and walking and relieved by sitting or bending over.  This problem may be helped with postural advice and exercises or it may need a surgical opinion, your health care professional/physiotherapist can help you decide what it is the best option of you.

Chemical sensitization

Sometimes the nerves are irritated in the lateral opening by the presence of certain chemicals that may be released following a tissue strain or a pain flare. This may cause similar symptoms to nerve compression, however the symptoms are often intermittent and improve with time.  Your physiotherapist/health care professional can assist with the diagnosis of leg pain associated with local chemical sensitisation and can recommend treatment and exercise that may help.  They will also be able to guide you with appropriate postural advice and activity modification to keep you active.

Non nerve related leg pain

Structures in the back such as ligaments, muscles, joints and discs can refer pain to the leg, therefore not all leg pain associated with back pain is caused by your nerves.  This is known as somatic referred pain.  You may be aware that people suffering with a heart attack can present with left sided arm, neck and jaw pain as well as pain in the heart area — this is a somatic referral pattern of the heart and an example of how non-nerve tissue can create pain elsewhere in the body.  It is important to understand the source of the leg pain as there are various treatment measures that may help including local manual therapy, postural advice and exercise.

Presence of central sensitization

Leg pain may be caused by more wide spread sensitisation of the nervous system and it is associated with persistent or chronic non-specific low back pain.  Sensitisation of the nervous system may be associated with non-physical factors such as sleep disturbance, sustained high stresslevels, depressed mood and anxiety.  There also may be the presence of other painful conditions such as fibromyalgia, chronic headaches, chronic menstrual pain, endometriosis as well as irritable bowel syndrome and irritable bladder syndrome.  If these conditions are present, it is important that your physiotherapist/healthcare professional spends time discussing them during your interview and they may ask you to complete some questionnaires to find out how they relate to your leg pain.

Lear more about Alison Low by visiting http://www.opsmc.com.au/person/alison-low/