Slipped disc

What is a slipped disc?

Above and side views

In a "slipped disc", a disc does not actually slip. There are two processes that can be known as a slipped disc:

• Part of the inner softer part of the disc (the nucleus pulposus) pushes out (herniates) through a weakness in the outer part of the disc. This is why prolapsed disc or herniated disc are better terms.

• Sometimes the outer layer of the disc bulges out because the disc has become less flexible over time. This is called a disc bulge.

In either case, the protruding part of the disc may press on nearby structures such as a nerve root coming from the spinal cord. Some inflammation also develops around the prolapsed part of the disc. Inflammation may irritate a nerve and also causes swelling, which may put pressure on a nerve.

Any disc in the spine can prolapse. However, 95 out of 100 prolapsed discs occur in the lower back (the lumbar spine). The size of the prolapse can vary. As a rule, the larger the prolapse, the more severe the symptoms are likely to be.

It is common for a prolapsed disc or disc bulge to be found on MRI scans in people with no symptoms at all.

Slipped disc symptoms

It is important to note that the size of slipped discs do not always correlate with symptoms. People with tiny disc bulges or slipped discs may complain of severe pain; people with big disc bulges or slipped discs may have very little pain. Slipped discs are often seen on MRI scans of people who have no back or leg symptoms at all.

Back pain

The pain is often severe and usually comes on suddenly. The pain is usually eased by lying still and standing and is often made worse when moving the back, coughing or sneezing.

Nerve root pain (sciatica)

Nerve root pain occurs because a nerve coming from the spinal cord is pressed on by a 'slipped' (prolapsed) disc, or is irritated by the inflammation caused by the prolapsed disc.

Although the problem is in the back, the pain can be felt anywhere along the course of the nerve in addition to back pain. The pain can go all the way down to the foot, depending on where the nerve is experiencing pressure. Nerve root pain can range from mild to severe but it is often worse than the back pain. People often describe nerve root pain as a burning or shooting pain.

With a prolapsed disc, the sciatic nerve is the most commonly affected nerve. The term sciatica means nerve root pain of the sciatic nerve. The sciatic nerve is a large nerve that is made up from several smaller nerves that come out from the spinal cord in the lower back. It travels deep inside the buttock and down the back of the leg. There is a sciatic nerve for each leg.

Other nerve root symptoms

The irritation or pressure on the nerve next to the spine may also cause pins and needles, numbness or weakness in part of a buttock, leg or foot. The exact site and type of symptoms depend on which nerve is affected.

No symptoms

Some people have a prolapsed disc without any symptoms. It is thought that symptoms mainly occur if the prolapse puts pressure on or irritates a nerve. This does not happen in all cases.

Cauda equina syndrome

Cauda equina syndrome is a serious type of nerve root problem that can be caused by a prolapsed disc. This is a rare disorder where the nerves at the very bottom of the spinal cord are pressed on. This syndrome can cause low back pain plus:

• Problems with bladder or bowel function (usually inability to pass urine but may also be incontinence of urine and/or faeces).

• Numbness in the saddle area around the genitals and back passage (anus).

• Weakness in one or both legs.

• Pain in one or both legs.

To read more about this condition, see the separate leaflet called Cauda equina syndrome.

How common is a slipped disc?

Only about 1 in 20 cases of back pain is caused by a "slipped disc", a prolapsed disc. (The majority are caused by muscle pains).

The most common age to develop a "slipped disc" is between 30 and 50 years. Twice as many men as women are affected. Disc problems are rare in anyone under 20 years of age.

Disc bulges are less likely to cause pain than prolapsed discs.

What causes a slipped disc?

As we get older, the discs in our backs become less flexible and more dry. This is called "disc degeneration". The discs are more prone to tearing. They are also more prone to bulging out of their normal position.

Various things may trigger the inner softer part of the disc to squeeze out through the weakened outer part of the disc. For example, sneezing, awkward bending, or heavy lifting in an awkward position may cause some extra pressure on the disc. In people with a weakness in a disc, this may be sufficient to cause a prolapse.

Factors that may increase the risk of developing a prolapsed disc include:

• A job involving lots of lifting.

• A job involving lots of sitting (especially driving).

• Strenuous physical activity or exercise.

• Smoking.

• Being overweight (obesity).

• Increasing age (a disc is more likely to develop a weakness as we become older).

• Genetics - some hereditary conditions or genetic factors may be linked to wear and tear of the discs.

How is a slipped disc diagnosed?

Slipped discs often have similar symptoms to back pain and leg pain caused by pressure on a nerve due to inflammation in a muscle. Examination can help to suggest that a "slipped disc" is a likely cause. In most cases, no tests are needed, as the symptoms often settle within a few weeks.

X-rays are not always useful as, whilst they can look at the vertebrae (bones in the spine), they cannot see the discs in between them. An MRI scan is effective at showing the site and size of a prolapsed disc.

It should be noted that, as explained above, it is known that people can have a disc prolapse without any symptoms. It is therefore very important to make sure that any prolapse seen on a scan matches up with the symptoms. Low back pain is very common and so can happen to someone who has a disc prolapse on their MRI scan but the disc prolapse is not the cause of the pain. See the separate leaflet called Lower back pain.

Slipped disc treatment

Stay active

People with a 'slipped' (prolapsed) disc should carry on as normal as far as possible. This may not be possible at first if the pain is very bad. However, it is important to move around as soon as possible and get back into normal activities as soon as you are able. As a rule, don't do anything that causes a lot of pain.

It is very important not to rest constantly, waiting for the pain to get better. People recover more quickly and are less likely to develop persistent (chronic) back pain if they keep active with back pain.

Sitting is often the most uncomfortable position with a "slipped disc" as this puts the most pressure on the nerve. Standing is often more comfortable so it is best to stand and walk as much as possible but then to lie whilst resting rather than sitting upright.

Exercise

General exercise is very important with a prolapsed disc. It can help lessen the pain by increasing the muscle strength for the muscles that support the spine.

Although it is not known if specific spinal exercises are better than generally keeping fit, a physiotherapist can advise on the best exercises for an individual.

Physical treatments

Some people visit a chiropractor or osteopath for manipulation and/or other physical treatments. It is debatable whether such physical treatments help all people with a prolapsed disc but they may provide some short-term comfort. They should be accompanied by regular exercise.

Medication

Painkillers, if needed, should be taken regularly. This is better than taking them now and again just when the pain is very bad. Regular painkillers mean that the pain is more likely to be eased for much of the time - this means that exercise and normal activities are easier and therefore recovery is faster.

• Anti-inflammatory painkillers. Some people find that these work better than paracetamol (see below). They include ibuprofen which can be bought at pharmacies or obtained on prescription. Other types such as naproxen need a prescription. Some people with asthma, high blood pressure, kidney failure, or heart failure may not be able to take anti-inflammatories.

• Weak opioid medicines (eg, codeine), with or without paracetamol, can be used for managing acute low back pain if an anti-inflammatory painkiller can't be used. However opioids should not be used as a long-term treatment for a slipped disc.

• A medicine for neuropathic pain, such as amitriptyline or gabapentin, is often prescribed if the pain has gone on for more than a few days. These medicines need to be taken regularly to be effective. Whilst these are not "normal painkillers" (they would not help for a simple headache for instance) they can be very helpful for pain which is coming from pressure on a nerve.

• Occasionally a muscle relaxant, such as diazepam, is also prescribed, usually if there is spasm in the muscles surrounding the spine. However, there is no evidence that diazepam is of any benefit in back pain, including from a slipped disc. Most doctors do not prescribe it for this reason and also because it can become addictive quite quickly, and can cause drowsiness. It is important not to drive when taking diazepam.

Epidural

An epidural is an injection given into the back. It is usually given into the area in the back around where the sciatic nerve comes out of the spine. It is performed by a specialist.

The injection contains a type of local anaesthetic and a steroid, which is a very strong anti-inflammatory. It is essentially a long-term painkiller that can give enough pain relief to enable starting or continuing to exercise.

Surgery

Surgery may be considered if the symptoms are very severe and have not settled after at least six weeks or so. This is the minority of cases as, in about 9 out of every 10 people with a prolapsed disc, the symptoms have eased off completely or are not bad enough to warrant surgery by this time.

The aim of surgery is to cut out the prolapsed part of the disc and release the pressure on the spinal cord and nerves. This often eases symptoms. However, it does not work in every case and therefore it is important to consider the potential risks and benefits of surgery.

The surgery tends to be more successful in people with:

• Very severe pain in the back and leg before surgery.

• A shorter time between the start of symptoms and the surgery.

• Younger age.

• Better mental health.

• Better pre-operative physical activity levels.

In the long-term, surgery and conservative treatment (painkillers and exercise) have the same results but surgery can work quicker than conversative treatment.

How long does a slipped disc take to heal?

In most cases, the symptoms tend to improve over a few weeks. About 50 out of every 100 people improve within 10 days, and 75 out of 100 after four weeks. 90 out of 100 are recovered by six weeks. In only about 2 out of every 100 people with a 'slipped' (prolapsed) disc is the pain still bad enough after 12 weeks that they end up having to have surgery.

Can a slipped disc be prevented?

Evidence suggests that the best way to prevent all back pain, including "slipped discs", is to keep active and to exercise regularly. This means general fitness exercise such as walking, running, swimming, etc.

There is no firm evidence to say that any particular back strengthening exercises are more useful than simply keeping fit and active. It is also sensible to be back-aware. For example, it is best not to lift objects when in an awkward twisting posture.

Understanding the back

The spine is made up of many bones called vertebrae. Each bone (vertebra) is roughly the shape of a flattened cylinder and between each vertebra is a disc. The discs are made of strong rubbery material which helps the spine to be so flexible. All the discs are the same - they have a stronger fibrous outer part and a softer jelly-like part in the centre called the nucleus pulposus.

The spinal cord contains the nerves that come from the brain. It is protected by the spine. Nerves from the spinal cord come out from between the vertebrae to relay messages to and from various parts of the body.

Strong ligaments attach to the vertebrae. These ligaments give extra support and strength to the spine. Various muscles also go around, and are attached to, various parts of the spine.