Mr Ben Okafor FRCS (Orth.)

Consultant Orthopaedic and Spinal Surgeon

What is a herniated disc?

Many patients with back pain, leg pain, or weakness of the lower extremity muscles are diagnosed with a herniated disc, or rupture of the intervertebral disc of the spine. When this occurs, the cushion that sits between the spinal vertebra is pushed outside its normal position. A herniated disc would not be a problem so often if it weren't for the spinal nerves that are very close to the edge of the intervertebral disc.

The intervertebral disc is a soft cushion that becomes more rigid with age. In a young individual, the disc is soft and elastic, but like so many other structures in the body (such as tendons and ligaments), as we age, the disc loses its elasticity and is more vulnerable to injury. In fact, even in individuals as young as 30, an MRI shows evidence of disc deterioration in about 30% of people.

When a herniated disc bulges out from between the vertebrae, the spinal nerves and spinal cord can become pinched. There is normally a little extra space around the spinal cord and spinal nerves, but if enough of the herniated disc is pushed out of place, then these structures may be compressed.

What causes symptoms of a herniated disc?

When the herniated disc ruptures and pushes out, the nerves may become trapped. A herniated disc may occur suddenly during a fall or an accident, or may occur gradually with repetitive straining of the lumbar spine. Often people who experience a herniated disc already have lumbar spinal stenosis, a problem that causes bone spurs and inflammatory tissue to take up some of the precious space around the nerves. When a herniated disc occurs, the space for the nerve is diminished and irritation of the nerve results.

Common symptoms of a herniated disc 

Leg pain

Most commonly experienced over the outside of the thigh, the lower leg, or foot. Shooting pain may be experienced coming all the way down the leg, which patients often describe an 'electric shock' feeling.


This is the medical word for abnormal sensations such as tingling, numbness, or pins and needles. These symptoms may be experienced in the same region as painful sensations.

Muscle weakness

Because of the nerve irritation, signals from the brain may be interrupted causing muscle weakness, usually of the ankle. Nerve irritation can also be tested by examining the reflexes of the knee and ankle.

Bowel or bladder problems

These symptoms are important because it may be a sign of 'cauda equina syndrome', a possible condition resulting from a herniated disc. This is a medical emergency, and your should see your doctor immediately if you have problems urinating, having bowel movements, or if you have numbness around your genitals.

All of these symptoms are due to the irritation of the nerve from the herniated disc. By interfering with the pathway by which signals are sent from your brain out to your extremities and back to the brain, all of these symptoms can be caused by a herniated disc pressing against the spinal nerves.

How is the diagnosis of a herniated disc made?

Most often, your physician can make the diagnosis of a herniated disc by physical examination by testing sensation, muscle strength, and reflexes.

An MRI is commonly used to help diagnose a herniated disc. It is very important that patients understand that the MRI is only useful when used in conjunction with examination findings. It is normal for an MRI of the lumbar spine to have "abnormalities," especially as people age. Patients in their 20s may begin to have signs of disc wear, and this type of wear would be expected on MRIs of patients in their 40s and 50s. This is the reason that your physician may not be concerned with some MRI findings noted by the radiologist.

Making the diagnosis of a herniated disc, and coming up with a treatment plan depends on the symptoms experienced by the patient, the physical examination findings, and the x-ray and MRI results. Only once this information is put together can a reasonable treatment plan be considered.

Return to spine conditions page.

Axial MRI scan showing prolapsed disc


MRI scan of prolapsed disc

020 8709 7878