In some cases of back or leg pain corticosteroid injections may provide some relief and the mechanism may be that the steroid reduces any inflammatory process present in the tissues. Steroids inhibits inflammatory chemicals some of which have been found in elevated levels in operatively removed disc material from humans. Such inflammatory mediators may promote disc degeneration and make the fibres of the annulus more sensitive to stresses. Other chemicals may add to disc related pain problems by making pain nerves more sensitised, reducing synthesis of the water holding proteoglycan chemicals in discs and by increasing the degrading effects on the disc matrix.
The motion segments of the lumbar spine contain nerve structures which can become over-sensitive and over-reactive, leading to painful sensations resulting from what were previously painless mechanical inputs. Radicular pain or nerve root pain is leg pain which may be the result of compression, inflammation or irritation of one of the nerve roots emerging from the spinal cord. The underlying pathology of nerve root pain is not clear, with suggestions being biochemical activators, inflammation, compromised blood supply and dysfunction of the axons secondary to compression. Compression injuries and internal swelling may be more likely to occur in spinal nerve roots due to their structure.
Compression of the nerve root may allow increased inflow of fluids to the nerve, resulting in oedema of the nerve which gives a higher internal fluid pressure. This can compromise the flow through local capillaries and cause the nerve to become fibrosed. Since around sixty percent of the nutrition of the spinal nerve roots is provided by the cerebrospinal fluid, any fibrosis of the nerves can reduce this and make them more liable to suffer symptoms of compression due to their increased sensitivity. Pain could be generated by the nerve alterations caused by slowing or interruption of the blood throughput, rather than the sensory and motor loss following peripheral nerve compression.
If the nerve and its vascular supply are compromised quickly then nerve root symptoms are more likely than with a slow onset, perhaps giving a clue to why older people do not suffer such symptoms despite compromise of the nerve exits. Disc material has been experimentally placed in the epidural space of dogs and found to generate a significant inflammatory reaction and may cause damage to nerves when in contact with them. If TNF (tumour necrosis factor) is injected into a nerve it causes similar changes to those which ensue after nerve root compromise. An auto-immune reaction to the internal disc material, which is not normally accessible, has also been proposed but it is likely that many aspects are relevant.
The spinal facet joints are formed from a joint process of a vertebra above and one below and are synovial joints like many other bodily joints. These joints respond to damage and injury like the rest of our joints and exhibit stiffness, pain, movement loss, muscle spasm and finally degenerative changes. The facet joints develop degenerative changes secondary to the changes which occur in the disc segments themselves. The facet joint capsules, well innervated fibrous bags, have been shown experimentally by injection to be able to refer pain into the legs, thoracic spine and arms, depending on their location. Established sources of pain, facet joints are known to be involved in large proportions of neck, lumbar and thoracic pain.
The sacro-iliac joint between the pelvis and the sacrum is a large synovial joint known to refer painful and other symptoms to the groin, the leg, low back and buttock. In patients with chronic low back pain, experimental testing has shown involvement of the sacroiliac joint in their pain problems in from two to thirty percent of cases. Pain receptors exist in muscular tissue also and respond to stretching and pressure as well as other inputs. If muscles are overburdened either repetitively or in a strain at one point they will respond by shortening, increasing their tension and being painful.
Myofascial pain sydrome has been described in injured or posturally abnormally used muscles, whereby muscles have an increased degree of contraction and so-called trigger points. Trigger points are firm, tender nodules felt on palpation in the muscle tissue and such palpation causes pain to radiate into local well defined areas. - 14130
The motion segments of the lumbar spine contain nerve structures which can become over-sensitive and over-reactive, leading to painful sensations resulting from what were previously painless mechanical inputs. Radicular pain or nerve root pain is leg pain which may be the result of compression, inflammation or irritation of one of the nerve roots emerging from the spinal cord. The underlying pathology of nerve root pain is not clear, with suggestions being biochemical activators, inflammation, compromised blood supply and dysfunction of the axons secondary to compression. Compression injuries and internal swelling may be more likely to occur in spinal nerve roots due to their structure.
Compression of the nerve root may allow increased inflow of fluids to the nerve, resulting in oedema of the nerve which gives a higher internal fluid pressure. This can compromise the flow through local capillaries and cause the nerve to become fibrosed. Since around sixty percent of the nutrition of the spinal nerve roots is provided by the cerebrospinal fluid, any fibrosis of the nerves can reduce this and make them more liable to suffer symptoms of compression due to their increased sensitivity. Pain could be generated by the nerve alterations caused by slowing or interruption of the blood throughput, rather than the sensory and motor loss following peripheral nerve compression.
If the nerve and its vascular supply are compromised quickly then nerve root symptoms are more likely than with a slow onset, perhaps giving a clue to why older people do not suffer such symptoms despite compromise of the nerve exits. Disc material has been experimentally placed in the epidural space of dogs and found to generate a significant inflammatory reaction and may cause damage to nerves when in contact with them. If TNF (tumour necrosis factor) is injected into a nerve it causes similar changes to those which ensue after nerve root compromise. An auto-immune reaction to the internal disc material, which is not normally accessible, has also been proposed but it is likely that many aspects are relevant.
The spinal facet joints are formed from a joint process of a vertebra above and one below and are synovial joints like many other bodily joints. These joints respond to damage and injury like the rest of our joints and exhibit stiffness, pain, movement loss, muscle spasm and finally degenerative changes. The facet joints develop degenerative changes secondary to the changes which occur in the disc segments themselves. The facet joint capsules, well innervated fibrous bags, have been shown experimentally by injection to be able to refer pain into the legs, thoracic spine and arms, depending on their location. Established sources of pain, facet joints are known to be involved in large proportions of neck, lumbar and thoracic pain.
The sacro-iliac joint between the pelvis and the sacrum is a large synovial joint known to refer painful and other symptoms to the groin, the leg, low back and buttock. In patients with chronic low back pain, experimental testing has shown involvement of the sacroiliac joint in their pain problems in from two to thirty percent of cases. Pain receptors exist in muscular tissue also and respond to stretching and pressure as well as other inputs. If muscles are overburdened either repetitively or in a strain at one point they will respond by shortening, increasing their tension and being painful.
Myofascial pain sydrome has been described in injured or posturally abnormally used muscles, whereby muscles have an increased degree of contraction and so-called trigger points. Trigger points are firm, tender nodules felt on palpation in the muscle tissue and such palpation causes pain to radiate into local well defined areas. - 14130
About the Author:
Jonathan Blood Smyth, editor of the Physiotherapy Site, writes articles about Physiotherapy, back pain, orthopaedic conditions, neck pain, injury management and physiotherapists in Bristol. Jonathan is a superintendant physiotherapist at an NHS hospital in the South-West of the UK.
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