Back pain can occur anywhere along the spine, but the most common site is the lower back or lumbar region. The lower part of the back bears the weight of the upper body as well as any weight you’re carrying. It also twists and bends more than the upper back.
Back pain may be acute, recurrent or chronic. Most cases of back pain are acute – i.e. the pain starts suddenly and intensely – and usually last a short time (less than a month).
Acute back pain is not usually caused by a serious medical condition and most cases resolve within a few days. Recurrence is however common and takes the form of repeated episodes of acute pain with pain-free intervals in-between.
Chronic back pain is present all the time, persists beyond three months and even slight movements can trigger it. Recurrent or chronic pain is usually more intractable than acute pain and often requires specialist advice.
Structure of the back
The back's system of bones, muscles, ligaments, tendons and nerves work together to bear the weight of your body and the loads you carry. The structure of the back provides considerable strength and flexibility, but because the spine is so central to the body's movements, even small amounts of damage can often cause pain.
The spine consists of 33 bony segments, the vertebrae. There are seven cervical, 12 thoracic, five lumbar, five sacral and four coccygeal vertebrae. The two latter groups – the sacrum and coccyx – are fused and immobile. Between the cervical, thoracic and lumbar vertebrae lie the discs: tough, spongy "cushions" that act as shock absorbers for the vertebrae and give the spine flexibility. Strong elastic ligaments hold the vertebrae and discs firmly together in a column. Muscles attach to the vertebrae by fibrous connections called tendons. The complex layers of back muscle contract to move your back and upper body.
The spine column also protects the spinal cord, which runs down through a canal formed by the vertebrae. Nerves (roots) from the spinal cord branch out and leave the spine through spaces between the vertebrae at the levels of the discs.
Who gets back pain and who is at risk?
Back pain is second only to headaches as the most common site of pain. Four out of five adults will experience at least one bout of back pain in their life.
The following factors can increase your risk for back problems:
Ageing: discs begin gradual deterioration from age 30. With age, the discs lose moisture and shrink. This puts more stress on the facet joints which become arthritic, with resultant back pain.
Sedentary lifestyle: being unfit increases your risk for back pain, especially if you attempt an unaccustomed activity. Lack of exercise leads to the following conditions which may threaten your back:
- muscle inflexibility: restricts the back's ability to bend and rotate.
- weak back muscles: increase load on the spine and the risk of disc bulge.
- weak stomach muscles: increase strain on the back and cause the pelvis to tilt abnormally.
- obesity: increases weight on the spine and pressure on the vertebrae and discs. A large belly pulls the spine forward and out of alignment, increasing the risk of back strain.
Poor posture and spending long periods in one position, such as working at a computer or slouching in front of the TV.
Genetic factors: some people are genetically susceptible to back pain, usually because they inherited spinal structural abnormalities. Mutation of the COL9A2 gene may be linked to about 10% of sciatica cases. This gene plays a role in producing collagen, an important protein component of the discs. The defective gene may cause disc deterioration, leading to sciatica.
Work that stresses the back: risky activities include lifting, forceful movements, bending and twisting into awkward positions, repetitive movements and vibration (as occurs with long-distance truck driving).
Improper body mechanics during sporting activities can damage the back, e.g. a jerky golf swing or incorrect use of exercise equipment. Cyclists often experience low back pain, which is often resolved by adjusting the angle of the bicycle seat. Some research suggests that, over time, high-impact exercise such as rugby or aerobics may increase the risk for degenerative disc disease. Hyperextension of the spine as in gymnastics and cricket (especially in the case of bowlers) may lead to a stress fracture (spondylolysis).
Pregnancy makes women prone to back pain due to shifting of abdominal organs, forward redistribution of body weight and loosening of ligaments in the pelvic area prior to delivery.
Smoking: possibly because it decreases blood circulation to the tissues of the back. The association may also be due to a generally unhealthy lifestyle.
Psychological factors: research indicates that in many people, pre-existing depression and feelings of helplessness may have a negative influence on one’s perception of pain and one’s ability to cope with back problems. People with depression are also more likely to have vague physical symptoms, including back pain.
Reviewed by Dr Pradeep Makan, orthopaedic surgeon, Melomed Gatesville and Life Vincent Pallotti Hospital in Cape Town and part-time lecturer in the department of orthopaedic surgery at the University of Cape Town, 2010.