Specific tissues tend to cause pain in characteristic areas. Many tissues cause pain in their local area, for example most joints will cause pain locally. Did you know – A common exception is the hip joint which frequently causes pain in the thigh or even the knee?
Conversely, many organs in the body cause pain at a distance from the source of the pain. For example, the heart commonly causes pain that is felt in the left arm. This is not because the heart presses on a nerve going to the arm but as a result of the brain incorrectly localising the heart in the arm. The gallbladder acts in a similar way and causes pain that is experienced in the right shoulder.
Sciatica is also termed a ‘referred pain’ and arises because any impingement or pressure on the sciatic nerve excites it and the brain thinks anything that comes from that nerve, comes from the leg. Similarly, brachalgia is a type of referred pain as it arises as pressure excites the cervical nerve roots and the brain thinks anything that comes from that nerve, comes from the arm.