The lumbar nerve roots emerge from the spine and at this point they are vulnerable to impingement from a disc prolapse, causing inflammation and/or compression of the nerve and the symptoms of sciatica. Sciatic leg pain is not common, affecting 3 to 5% of adults and both sexes equally. Men are more likely to get it in their 40s and women in their 50s, with pain symptoms lasting over six weeks in up to a quarter of cases. Physiotherapists are routinely asked to supervise the management of sciatica.

A "slipped disc" is the result of the outer wall of the disc (the annulus) developing a split through which the central material (nucleus) partly herniates. The prolapse can directly compress the passing nerve root, damaging the nerve through pressure and from the irritant chemicals in the nuclear material. This can alter and obstruct the nerve's normal electrical activity and block the circulation which leads to swelling. While true sciatica is typically caused by disc prolapse the size of the prolapse does not relate the level of suffering experienced.

The great forces which we impose on the low back mean the lumbar intervertebral discs suffer structural changes and prolapses. Many activities involve a significant level of leverage, such as flexing over, performing movements in an upright position and lifting with the arms away from the body. This greatly magnifies the forces on the discs and due to their fluid mechanics they suffer 3-5 times the loads on the skeleton. This can cause the disc walls to degenerate, giving weak areas and predisposing to prolapse at some time.

Patients report that the onset of sciatica is rapid and accompanied by back pain, although pre-existing back pain may ease when the leg pain starts. Worse with coughing, sneezing and sitting down, the pain is better standing up or lying flat. Typical pain distribution is through the buttock then down the back of the leg to the ankle and foot or down the side instead. Sciatica does occur in disc levels L1 to L3 but only in for five percent of cases, the pain being in the front of the thigh and not in the lower leg. Some patients present with individual areas of pain rather than the whole picture.

The physiotherapist will take the patient's history with particular attention to "red flags" which are indicators of a serious medical reason for the back pain and the patient will not be appropriate for physio. Weight loss, fever, night sweats, age (under 20 or over 55), problems with bladder and bowel control, serious past medical history and night pain will be noted. Any uncertainty means referral to a doctor for investigation. The physio will note any postural abnormalities and the nature, position and activity response of the pain symptoms.

A patient with lumbar radiculopathy may exhibit abnormal posture, sometimes bent forward and unable to bend backwards, with a one-sided trunk shift. Physiotherapists check the ability to perform spinal movements, any pattern of limitation or tendency for the pain to centralise on repeated movements. Physios will test the reflexes, sensibility and muscle power to perform the neurological examination. This and the straight leg raising test allow the physio to check which of the spinal nerves is likely to be the culprit.

Discogenic pain may change with repeated movements, spreading more towards the leg or in towards the back, the latter being called centralisation. Physiotherapists use this phenomenon to diagnose and treat disc related back pain and examine the joints of the lower limb as thigh and knee pain can be referred from an osteoarthritic hip joint. A full history and examination both eliminates patients who need medical referral for investigation and allow the physio to form a treatment strategy.

Physiotherapy sciatica treatments include many therapies: manipulation, mobilisation technique, lumbar stability, myo-fascial release, McKenzie method (especially useful in disc prolapse), stabilising exercise, massage and soft tissue techniques, pain killers, education of the patient, advice on the best position to relieve extreme sciatica pain and rest. Sciatica settles as the pressure and inflammation ease but physiotherapists would recommend an ongoing exercise programme to maintain back fitness over the long term.