Pain may occur when tissues do not get enough blood (a condition called ischemia). Pain occurs because the tissues do not get enough oxygen, which is carried to tissues by the blood, and because waste products, which are carried away from tissues by the blood, accumulate.
If blood flow is completely blocked, as from a blood clot in a large artery, severe constant pain occurs suddenly, and the affected arm or leg becomes pale and cool. If blood flow is only partly blocked, as may occur with atherosclerosis (usually a problem in the legs), the person usually feels a tightening, fatiguing pain in the calf muscle during physical activity. This pain, called claudication, is rapidly relieved by rest and comes back during similar activity.
Pain in the limbs may also result from strained muscles, injury to certain nerves near the spinal cord, formation of blood clots in veins (venous thrombosis), or skin or muscle infections. If doctors suspect that the pain is caused by a blood vessel disorder, ultrasonography to evaluate blood flow in the affected area may be done.
Last full review/revision April 2006 by Paul H. Tanser, MD