Only about 5% of people with lower back problems will have a pinched sciatic nerve. Most people will have non-specific or simple lower back pain. So don’t automatically assume that because you have pain in your back or buttock that it is sciatic nerve pain.
Sciatica is most often caused by spinal disc problems. Sometimes the disc bulges backwards and to the side causing a compression or irritation of the nerve as it leaves the spinal cord. Occasionally the centre of the disc will prolapse completely out of the disc wall.
It is unusual to feel sciatica symptoms just in the back, even though sciatica is caused by irritation of the sciatic nerve just as it leaves the spine . Instead it is more common to feel sciatic pain along the ‘distribution’ of the nerve - or in other words in the area that the compressed or pinched nerve supplies.
Where the symptoms are felt depends on which nerve root has been pinched or irritated. It is possible to have a reasonable guess at this by looking at something called a dermatome chart (see below). This chart gives us an approximation of where the pain is normally felt when a specific nerve is irritated.
Dermatome Chart showing where pinched nerve pain is often felt
The diagram below shows the two most common areas that are affected. These are the last 5th Lumbar and 1st sacral nerve root, also called level L5/S1 (shown on the right) and also the level above at the junction of the 4th and 5th Lumbar vertebrae, this one is refereed to as L4/5 (shown on the left)
The two most common places to feel pinched nerve pain
Sciatic nerve pain is generally felt in the buttock, thigh and calf. Sometimes the symptoms will also be felt in the foot.
It is not at all uncommon for someone with pinched sciatic nerve symptoms to have no lower back pain at all.
If the nerve is irritated enough it can also lead to changes in the way your legs feel and how strong they are. These changes are called ‘neurological changes'.
In addition to pain, symptoms commonly include leg and foot tingling and numbness and sometimes weakness.
Sometimes, if the nerve is very affected it can interfere with how it works. When I am assessing someone that I think might have sciatic nerve pain I look to see if the things that the nerve controls are affected at all. I do this by checking the different functions of the nerve.
You may not notice some of these symptoms until you are checked by a doctor or physical therapist.
Sensation (feeling) is changed
It is common to feel altered sensation such as pins and needles, tingling and numbness in the leg or foot.
This is tested by checking light touch and pinprick sensation - often there is a difference between sides.
Power (strength) may be weaker
The sciatic nerve transports nerve impulses from the brain to the muscles in the hip and legs and back again.
If the nerve roots are compressed or badly irritated you may have a feeling of weakness in the leg or foot. When walking you might notice its a bit hard to push off with your toes, or you might notice a foot drop (difficulty clearing the ground with your toes).
Reflexes (reduced or lost)
Reflexes are tested with a reflex hammer. The one at the knee tests the L3 reflex, the reflex at the ankle is the S1 reflex and this is the one that is most often affected.
Symptoms may include a complete loss of the reflex or sometimes it is just diminished.
Testing the L3 or knee reflex. The process is the same at the ankle.
Occasionally a disc bulge is very severe and actually presses on the lower part of the spinal cord – the cauda equina. This is a surgical emergency. Symptoms include :
This page on cauda equina syndrome will tell you more. Make sure if you have any of these symptoms that you talk straight away to a medical professional.
Read more about sciatic nerve symptoms