Most people suffer from backache at times during their lives, much of which has no identifiable cause – non-specific back pain. This diagnosis is one of the biggest single causes of sickness absence in the UK's working population. Certain occupations, such as those involving long periods of sedentary work, lifting, bending and awkward physical work, are especially likely to cause backache. Back pain is commonly the result of sporting activities.

Non-specific back pain is probably the result of mechanical disorders in the muscles, ligaments and joints of the back – torn muscles, sprained LIGAMENTS, and FIBROSITIS. These disorders are not always easy to diagnose, but mild muscular and ligamentous injuries are usually relieved with warmth, gentle massage, analgesics, etc. Sometimes back pain is caused or worsened by muscle spasms, which may call for the use of antispasmodic drugs. STRESS and DEPRESSION (see MENTAL ILLNESS) can sometimes result in chronic backache and should be considered if no clear physical diagnosis can be made.

If back pain is severe and/or recurrent, possibly radiating around to the abdomen or down the back of a leg (sciatica), or is accompanied by weakness or loss of feeling in the leg(s), it may be caused by a prolapsed intervertebral disc (‘slipped disc’) pressing on a nerve. The patient needs investigation, including MRI. Resting on a firm bed or board can relieve the symptoms, but the patient may need a surgical operation to remove the disc and relieve pressure on the affected nerve.

The nucleus pulposus – the soft centre of the intervertebral disc – is at risk of prolapse through an acquired defect in the fibrous cartilage ring surrounding it. Over the age of 40 this nucleus is firmer and ‘slipped disc’ is less likely to occur. Once prolapse has taken place, however, that segment of the back is never quite the same again, as OSTEOARTHRITIS develops in the adjacent facet joints. Stiffness and pain may develop, sometimes many years later. There may be accompanying pain in the legs: SCIATICA is pain in the line of the sciatic nerve, while its rarer analogue at the front of the leg is cruralgia, following the femoral nerve. Leg pain of this sort may not be true nerve pain but referred from arthritis in the spinal facet joints. Only about 5 per cent of patients with back pain have true sciatica, and spinal surgery is most successful (about 85 per cent) in this group.

When the complaint is of pain alone, surgery is much less successful. Manipulation by physiotherapists, doctors, osteopaths or chiropractors can relieve symptoms; it is important first to exclude a serious disorder such as a fracture or cancer.

Other local causes of back pain are osteoarthritis of the vertebral joints, ankylosing spondylitis (an inflammatory condition which can severely deform the spine, see SPINE AND SPINAL CORD, DISEASES AND INJURIES OF), cancer (usually secondary cancer deposits spreading from a primary tumour elsewhere), osteomyelitis, osteoporosis, and PAGET'S DISEASE. Fractures of the spine – compressed fracture of a vertebra or a break in one of its spinous processes – are painful and potentially dangerous. (See BONE DISORDERS.)

Backache can also be caused by disease elsewhere, such as infection of the kidney or gall bladder (see LIVER), inflammation of the PANCREAS, disorders in the UTERUS and PELVIS or osteoarthritis of the HIP. Treatment is effected by tackling the underlying cause. Among the many known causes of back pain are: