Sciatica - Causes 

Causes of sciatica 

Sciatica: animation

Sciatica causes pain that radiates out from the lower back, down the buttocks and into one or both of the legs, right down to the calf. This animation explains what sciatica is and what causes it.

Media last reviewed: 18/01/2013

Next review due: 18/01/2015


Everything you need to know about this lower back condition

Sciatica occurs when the sciatic nerve, which runs from your back to your feet, becomes compressed or irritated.

There are many reasons why this may happen, although the vast majority of cases are caused by a herniated or "slipped" disc.

Herniated ('slipped') disc

Your spine is made up of vertebrae, discs and nerves. Vertebrae are the blocks of bone that make up the structure of your spine and protect the nerves.

The vertebrae are supported and cushioned by discs. These discs are made from a tough, fibrous case that contains a softer, gel-like substance. A herniated disc occurs when the outer part of the disc ruptures (splits), allowing the gel inside to bulge and protrude outwards between the vertebrae. When this presses against the sciatic nerve, it can cause sciatica.

It is not always clear what causes a disc to break down, although age is a common factor. As you get older, your spinal discs start to lose their water content, making them less flexible and more likely to rupture  this is sometimes called "degenerative disc disease".

Spinal stenosis

Spinal stenosis is the narrowing of the passage where the spinal cord travels down the spine.

It occurs when the ligaments become overgrown, but bulging of spinal discs and bony spurs from the vertebrae can also contribute. The sciatic nerve is only occasionally affected, meaning that the symptoms tend to be pain in a person's lower back, with heaviness of the legs, a stooped posture and difficulty walking.

Spinal stenosis is usually caused by age-related changes in the spine, but can also be down to degenerative disease of the spinal joints, which causes the vertebrae to lose their correct alignment.


Spondylolisthesis occurs when a vertebra slips out of position. If the slipped vertebra compresses the sciatic nerve, it can cause sciatica.

Spondylolisthesis is most commonly caused by age-related or degenerative wear of the spinal joints. However, in younger people, it can be caused by spinal fractures and repeated excessive bending of the spine.

Other causes

Less commonly, sciatica may be caused by:

  • an infection in the spine
  • an injury to the spine, or the surrounding muscles and ligaments
  • a growth within the spine, such as a tumour
  • cauda equina syndrome (see below)

Cauda equina syndrome

Cauda equina syndrome is a rare but serious condition that can cause sciatica.

The cauda equina is the bundle of nerves that lead out from the end of the spinal cord. Cauda equina syndrome occurs when these nerves are compressed and damaged. It can eventually lead to paralysis if left untreated.

One of the warning signs of cauda equina syndrome is suddenly losing control of your bladder or bowels. If this happens, you should call 999 for an ambulance immediately.

Page last reviewed: 26/08/2014

Next review due: 26/08/2016


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The 8 comments posted are personal views. Any information they give has not been checked and may not be accurate.

Rienzi said on 03 February 2013

After months of pain and advice from physiotherapists and my GP (all to no avail), I stopped all but essential exercise and experienced an immediate improvement but, best of all, I found that, if I lay flat on the floor with a small cushion under my lower back, with my buttocks just toucing the floor, after five to ten minutes there was a dramatic improvement. After three days the pain in my calf had completely gone and I could walk properly again for the first time in almost a year.

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sybilo said on 24 December 2011

I can relate to these comments people do seem to think that sciatica is nothing. I crawled around my bungalow for weeks before I saw any real improvement hanging onto the walls and furniture in agony. shooting pains throbbing down leg into my ankle it's just too much.

I have connected myself the coccyx with arthritis and couda equina where all the nerves meet at the bottom of the spine. I cannot find out if permanent damage can be done by constantly injuring this area in this way
paralysis is frightening even though it may be only temporary you always have the fear that one day it may become permanent

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sybilo said on 24 December 2011

there is a spelling mistake on there fibrous case that

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fransmark said on 07 November 2011

hi im feed up with drs i had my first mri scan in 2009 showing that L2/3/4/5/S1 discs are degenerate also facet joint arthrosis at L4/5/S1 which when they told me i thought so now what she said that it is like arthritis of spine and basically to just get on with it Then march of this year i pulled my back docs sents me for a mri scan which after being forgot about twice i finally got my scan in may which came back with a disc bluge and the sciatica was the most painfully i had known Consultant said i didnt warrant surgery as it is small and i was too young im 40 so i was to have epidural steroid injections a set of 3 can be given i had my 1st in sep 2 days of pain relief and then back to pain im due to see consultant tomorrow morning my GP thinks i should have surgery as injection never worked but not sure what consultant will think ? i have to work as i need the money but after work im in so much pain i have no family life used to love walking the dogs with my husband i do try but the pain is terrible so is this how my life is to be sorry for the rant xx

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mollystarlight said on 15 July 2011

My specialist said that if the hips are in pain the rest of the back will suffer, posture etc.(my friend whom I hadn't seen for a year asked me 'why are you stooping'. I was compensating for the pain and didn't realise how much forward I was leaning. I had a birmingham hip replacement and thankfully the excruiating pain and locking of the joint was completely cured. I am looking to have the other side done also as I have sciatica in it, which I didnt have in the right hip. My advice is the sooner something is done to correct the pain, the more successful it will be as there will be less wear and tear on the joints and spine. Luckily I'm with Bupa.

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Rob1822 said on 12 October 2010

Most people I speak to say its a waste of time going there (GPs). After 31 weeks of listening to different doctors (I can never get to see the same one!) giving their own take on it, prolapsed disc by one, displaced nerve catching on the bone (with little plastic spine for illustration) by another, I kept pushing for an MRI scan and eventually, after speaking with a MSK professional who knows about sciatica, I had one on week 31, it showed a Synovial cyst of a substantial size on facet joint right L5 affecting Right L4 / L5. These cyst’s come as the spine degenerates with age, it is thought that the bone produces too much ‘lubricant’ because of the rough bone, this builds up and forms a cyst, apparently it can be removed or burst, this is the stage I am at now! If you Google “Synovial cyst” you will find out more. I found a deep massage was a great help with the leg pain, hurts at the time but worth it.

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sofiabu said on 17 May 2010

Please, please when will the NHS look into piriformis sciatica.? I have suffered with thisdreadful pain for over six years. Three NHS G.P's and six NHS physiotherapist have not believed it exists.... but it does. It is very simple to diagnose.
Thank you

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suebee50 said on 14 January 2010

I have been suffering with osteoarthritis in my hip for a few years it is now classed as in an advanced state and needs replacing. I have been in excrutiating pain on and off over the last six months and reading all your comments proves that I am also suffering from sciatica, reading the pain you are going through is like reading my own symptoms. My specialist did say there was a lot of wear and tear in my lower back which would be more likely to cause the pain than the hip joint, yet sciatica has never been diagnosed despite me trying to explain the symptoms to my GP. I notice that in the causes it mentions slipped discs but there is no mention of osteoarthrits does anyone else feel the arthritis can also cause sciatica.
Not sure where to go from here, but I am finding life v. difficult as I cannot be on my feet for more than half an hour without pain, if I try to push past the pain barrier, I get into such a state that everything seems to lock up and be on fire. cant stand, sit or walk without crying in pain. I wish the gps would be more sympathetic with people like us who suffer like this. As some of you have said. in the 21st Century why isnt there a reliable treatment for this complaint.

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