Pain is the body’s warning system. It tells you something is wrong and prompts you to take action to tackle the problem. Sometimes the sensation appears to come from an area of the body other than the source of the pain.
If you accidentally try to pick up a hot saucepan, you feel pain in your hand and quickly snatch it away. The nerves in your hand flash a warning to the brain via the spinal cord that damage is occurring and the brain replies by telling the muscles to move the hand out of danger – fast. The pain is not really in your hand, it just feels that way. This is because the nerve supplying the hand, like all nerves in the body, has no “feeling” of its own. Its job is to transmit information in the form of an electrical current to the brain. The brain then interprets that information and labels it “pain”. Because the pain signal is being transmitted by the nerve which supplies the hand, the brain labels it “pain in the hand” and that is how you consciously experience it.
This system normally works very efficiently but, in certain I circumstances, it can lead to confusion. If, for instance, the root of the nerve that supplies the hand is compressed by a structural problem such as a prolapsed disc, the pain may be felt in the hand, not in the neck, where the disc actually is. This is because as far as the brain is concerned the nerve sending back the warning signal is the one that supplies the hand, so it labels the warning “hand pain”. This is known as referred pain.
Referred pain explains how ‘ghost pain” can occur. This is when people who have had limbs amputated frequently feel pain in the part of their body that is no longer there. The remainder of the nerve that used to supply the amputated arm or leg goes on sending its warning to the brain and the brain goes on labeling this message as arm or leg pain.
In the human back, referred pain can be felt anywhere along the pathway of a compressed nerve. If one of the nerves that run from the base of the neck to the hands is compressed, pain can be felt down the arm and into the hand. If one of the nerves that run from the base of the spine down the legs and into the feet is compressed, pain may be felt in a buttock, a leg or even a foot.
The site of the referred pain can give doctors and therapists valuable information about exactly where in the back the troubles lie. If you feel pain in the back of a thigh and down the outer side of your leg and foot, for example, the problem may be in the base of the spine at the level of the sciatic nerve roots. Pain in a buttock or in the groin may point to a problem at waist level, and pain down an arm may indicate compression of a nerve root in the upper chest or neck region of the spine.
Trigger Points
Small areas of muscle that have become chronically tense, perhaps following an injury, years of poor posture or even as a result of bottled-up anxiety, anger or frustration are known as trigger points.
The muscle fibers at these points are in a state of constant spasm and often radiate pain to areas far away. A trigger point in the lower back, for example, can cause pain in a buttock. Sometimes the trigger point is far less painful than the target area. Many people have back pain triggered by chronic muscle tension elsewhere, in the neck or shoulders perhaps, of which they are completely unaware. In such cases, the trigger point remains “silent” until or unless it is revealed by a manipulation therapist’s probing fingers.
Other Causes of Referred Pain
Just as structural problems in the back can refer pain to other areas of the body, disorders elsewhere can cause pain in the back. In these cases, however, there are usually other symptoms as well.
Kidney Problems
Your kidneys are responsible for filtering out waste products from your blood. Occasionally, deposits of hard mineral salts, or kidney stones, can form or the kidneys can become infected. Low back pain can be one of a number of symptoms in both cases. Kidney stones generally cause intermittent sharp pain in the lower back, along with nausea. Constant low back pain extending into the groin, accompanied by fever and discolored urine may indicate a kidney infection.
Gall Bladder Problems
The gall bladder concentrates bile secreted by the liver, before passing it into the digestive system, where it helps fat absorption. If too many stones of mineral salts form in the gall bladder, it may become inflamed. Pain is often felt in the lower tip of a shoulder blade, accompanied by abdominal pain, nausea and fever.
Pancreatitis
The pancreas lies on the left-hand side of your abdominal cavity, near your stomach. It has two roles: producing enzymes, that are important for the digestion of food; and manufacturing the hormone insulin, which regulates the amount of sugar in the blood. Heavy alcohol consumption can result in the pancreas becoming inflamed, a condition known as pancreatitis. This can cause pain in the top of the stomach and an intermittent, gnawing pain in the mid-back. This is sometimes accompanied by diarrhoea and, occasionally, by jaundice (yellowing of the skin).
