Back Pain - Assessment, Diagnosis &Treatment
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Lower Back Pain - Anatomy and Common Conditions


The Structure of the back

What is a slipped disc?


Cauda equina syndrome

Magnetic resonance imaging (MRI) scans

Computerised Tomography (CT) scan




The structure of the back

The back is a complex structure consisting of:

24 small bones (vertebrae), that support the weight of your upper body and form a protective canal for the spinal cord.

Shock-absorbing discs (intervertebral discs) that cushion the bones and allow the spine to bend.

Ligaments that hold the vertebrae and discs together.

Tendons to connect muscles to vertebrae.

A spinal cord, which carries nerve signals from the brain to the rest of the body.



The lower part of your back is known as the lumbar region, which is made up of five vertebrae, known as L1, L2, L3, L4 and L5. The lumbar supports the entire weight of your upper body (plus any extra weight that you are carrying), and it is under constant pressure, particularly when you are bending, twisting and lifting.

Slipped disc is the common name for the medical terms 'prolapsed' or 'herniated' disc.

A slipped disc most commonly occurs in people who are between 30 and 50 years of age. The condition affects twice as many men than women. Although back pain is a common problem for adults over the age of 30, a slipped disc is the cause of less than one in 20 cases of sudden back pain. Most back pain is the result of a muscle or ligament strain.

What are discs?

The discs you have in your back are protective, circular pads of cartilage (connective tissue) that lie in between the bones of your spine (vertebrae). The discs are responsible for cushioning the vertebrae when you jump or run. The discs are made from a tough, fibrous case, which contains a softer, gel-like substance.

The spinal cord is a collection of nerve fibres that are attached to the brain, and are protected by the spine. Nerve fibres from the spinal cord pass between the vertebrae, and take and receive messages to and from different parts of the body.

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What is a slipped disc?

A slipped disc occurs when the outer part of your disc ruptures, allowing the gel inside to bulge and protrude outwards from in between your vertebrae. The damaged disc can put pressure on your whole spinal cord or on a single nerve fibre. This means that a slipped disc can cause pain both in the area of the protruding disc and in any part of your body that is controlled by the nerve the disc is pressing on.

A slipped disc occurs most frequently in your lower back, but any disc can rupture, including those in your upper back and neck.

Some people who have a slipped disc experience no obvious symptoms. This is usually because the part of the disc which bulges out is only small, or it may not be pressing on the nerves or spinal cord.

However, many people who have a slipped disc do experience pain. Most will begin by experiencing pain in their lower back. The pain can then sometimes spread to other parts of the body.

It is not always clear what causes the tissue to break down. A lot of slipped discs are the result of increasing age. As you get older your spinal discs start to lose their water content, which makes them less flexible and more likely to rupture.

There are a number of other factors which can put increased pressure and strain on your spine. Some of these factors are outlined below:

bending awkwardly,

having a job that involves heavy, or awkward, lifting,

having a job that involves lots of sitting (particularly driving),


being overweight,

participating in a weight-bearing sport, such as weight lifting, and

having a traumatic injury to your back, such as a fall or car accident.

Factors such as these can weaken the disc tissue, and trigger a slipped disc.

Most cases of a slipped disc will not require further testing as symptoms will usually settle down particularly with osteopathy or physiotherapy treatment aimed at mobilising the joint, relaxing muscles which will take the pressure of the disc. However, if your symptoms do not ease after four to six weeks, then your GP may have to refer you for a series of tests to help rule out other conditions or to investigate the size and position of the slipped disc.

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With most slipped discs, pain is caused when part of the disc starts to press on one of the nerves that run along the spine. The sciatic nerve is the most commonly affected nerve. This large nerve is made up of several smaller nerves that pass from your spinal cord in your lower back. The nerve travels deep inside your buttocks and down the back of each leg.

If you have pressure on the sciatic nerve it can cause: a lasting, aching pain, numbness, and a tingling sensation in one, or both, of your legs.

These symptoms often start in your lower back and then travel down your buttocks and into either of the legs.


Other nerves

If the slipped disc presses on any of the other nerves that run down your spinal cord, your symptoms may include:

muscle paralysis, muscle spasms, and a loss of bladder control.

Muscle spasms and paralysis tend to occur in your arms, legs and buttocks. The pain you experience when a disc presses on a nerve is often worse when you cough or sneeze. This is because these sudden movements can put more pressure on the nerve. The pain can also be worse when you go to sit down because, again, pressure is put on the spine and nerves.

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Cauda equina syndrome

Cauda equina syndrome is a serious condition where the nerves at the very bottom of the spinal cord become compressed. The symptoms of the syndrome include:

lower back pain,

numbness in your groin,

paralysis of one or both legs,

rectum pain(pain in the lower bowel and anus),

bowel disturbance,

being unable to pass urine, and

pain in the inside of your thighs.

If you develop any of these symptoms, you should contact your GP immediately. If cauda equina syndrome is not promptly treated, the nerves to your bladder and bowel can become permanently damaged


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Magnetic resonance imaging (MRI) scans

An MRI scan uses a strong magnetic field and radio waves to produce detailed images of the inside of your body. This type of scan is very effective at showing the position and size of a slipped disc. It can also help your GP to pinpoint which nerves are being affected.

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Computerised Tomography (CT) scan

A CT scan involves a series of X-rays being taken which are later pieced together by a computer. This can help to produce cross sectional images of your spinal column and the structures which surround it. Like an MRI scan, a CT scan will help your GP to pinpoint a slipped disc, although it is often not as effective as an MRI scan.

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A myelogram is a test that involves injecting a special dye into the spinal fluid. An X-ray is then taken so that the specialist can look at the fluid. This test can show what pressure there is on the spinal cord or nerves as a result of a slipped disc. A myelogram can also detect other causes and conditions associated with back pain, such as a tumour, infection or arthritis. 

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