ABC of rheumatology. Low back pain.

Abstract

Low back pain is a major and increasing cause of disability in the United Kingdom. In 1993, 11% of the population reported that their activities had been restricted by back pain within the past four weeks. Satisfactory treatment of low back pain depends on an accurate diagnosis, but finding the cause for low back pain is often not possible because of difficulties in localising the source of the pain. In 1938 it was shown that many structures in the lumbar spine, when irritated, give rise to pain with very similar distributions. Despite technological advances the identification of an exact source of pain or an exact pathological diagnosis often remains elusive. It is important for doctors and patients to understand that the diagnosis of low back pain therefore depends on identifying some clinical syndromes on the basis of a patient's history and examination, with appropriate investigations to exclude serious pathology and support the clinical diagnosis. If this principle is misunderstood the result can be a misleading diagnosis and inappropriate treatment. Radiation of pain after injection of 0.1-0.3 ml 6% hypertronic saline into sacrospinal muscle (yellow) and multifidus muscle (red). Note similarity to distribution of sciatic pain. View this table: It is vital to distinguish mechanical causes of back pain from other causes as patients with mechanical causes are likely to respond to physical forms of treatment. The symptoms and signs of mechanical back pain differ considerably from those associated with back pain caused by underlying systemic disease. Most acute episodes of low back pain arise in the triad of joints that allow one vertebra to articulate with another (that is, the intervertebral disc anteriorly and the two facet joints posteriorly). The commonest primary pathology is degeneration of the nucleus pulposus in the lumbar disc. The disc itself is often not the source of pain; …