Chronic Low Back Pain
Low back pain can have many sources, one of which is the disc.
The discs sit between each vertebra in the spine and are similar to the cartilage in the knee. Their function is to allow movement of individual segments of the spine; aid the spine in weight bearing; shock absorbance and transmission of force from spine to pelvis to legs.
Discs are made up of two different substances: the firm outer ring, known as the annulus; and the semi-fluid gel interior, known as the nucleus. The main constituent of the disc is water. The nucleus is 85% water in the young, and 70% in the elderly. The annulus is 70% water.
Degeneration is an early ageing process that can affect the discs as well as joints (arthritis). The most commonly affected discs are the bottom two – L45 and L5S1.
The process of degeneration involves the reduction of the disc’s water content in the nucleus. Most of this process actually occurs in early adult life, although symptoms tend to occur later – mainly in the 30-50 age group. The annulus becomes harder, and loses layers, making it less thick and less resilient. The disc’s functions are therefore reduced.
As the disc thins, the vertebrae move closer together. This causes several problems:
- Structures between the vertebrae (other than the discs) can become compressed, causing pain.
- The ligaments and capsules surrounding the bones and discs become slack and cease to function correctly, limiting the amount of support the spine has.
- The disc itself is put under pressure as the vertebrae compress it. This can be enough to produce disc pain, especially as the spine has lost some of the supporting structures (ligaments, capsules) which help to relieve the pressure.
- The disc under increased pressure can be forced to bulge outwards. This will become hard and form little spurs of extra bone which can be seen on x-ray and are known as osteophytes. These can encroach on other structures, eliciting pain.
- As the disc becomes stiffer and under increased pressure, micro-fractures (small, horizontal cracks) can occur , further weakening it and increasing its susceptibility to injury.
Factors that contribute to disc degeneration are:
- Ageing – normal process
- Obesity – increases the pressure within the discs
- Sustained postures – can put excess pressure on structures
- Occupation – sustained positions / heavy lifting increases stress on spine
- Trauma – any previous spinal trauma can lead to degeneration later on
- Congenital abnormalities
- Hereditary – some just have a tendency towards early degeneration
Symptoms vary depending on which level of the spine is involved, and which structures if any are compressed:
- There is usually a dull ache in the low back. This may be constant, or alter with positions. Common aggravating postures are prolonged sitting or standing as the disc is under maximum pressure with little support (slackened ligaments and capsules).
- Referred pain may occur in the groin or leg. Again, this depends on level and structures involved, although discs themselves are able to refer pain, irrespective of compressing other structures.
- Reduced movement – pain or stiffness may restrict some movements.
- Early morning pain / stiffness. This is a common symptom. It may be related to a static position or choice of position for several hours, the type of mattress, or the fact that discs gain some water content overnight and therefore swell a bit, resulting in further compression by the vertebrae.
- Numbness / pins and needles in the legs or feet. This may occur if a nerve is compressed.
The easiest way to prevent degeneration is to maintain a healthy back. Avoid sustained, repetitive postures, especially stooping, bending or twisting; avoid repetitive heavy lifting; be aware of sitting postures – especially in the car and at work; regular, gentle exercise keeps a back fit – avoid repetitive high impact. For further details regarding posture and back care, refer to the information page titled Posture, Back Care and Neck Care. Pilates is an excellent form of exercise – it concentrates on the muscles which support the spine – this will enable the body to cope even if the ligaments and capsules in the spine have started to slacken.
If symptoms do develop, see your GP. He may give you some anti-inflammatories for the pain and may send you for x-rays.
Physiotherapy is an excellent form of treatment. It offers pain relief, and will give you advice and exercises to help support the spine and prevent any further recurrence of symptoms.