Leg Pain Overview
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While leg pain is a common occurrence after an injury, pain can also occur because of medical conditions or nontraumatic reasons. Pain in the legs may be due to injury or inflammation of any of the structures that are found in the leg, including bones, joints, muscles, tendons, ligaments, blood vessels, nerves, and skin. Inflammation of tissues is usually the cause of pain. Pain can also radiate from other parts of the body and be felt in the leg. Back ailments can cause pain and numbness of the leg. Abdominal aorta and iliac artery aneurysms can also present with leg pain. Blood clots in the large veins located in the abdomen are a further cause of leg symptoms.
Anatomy of the Leg
The structure of the leg begins with the skeleton. The large bones of the leg are the femur (thighbone) and the tibia and fibula of the shin. Smaller bones are found in the feet and toes. The patella (kneecap) is located in front of the knee joint where the femur and tibia meet. Major joints include the hip, knee, and ankle, but the small joints in the feet and toes also are important since they help support the body and cushion the force that is generated by walking and running.
The joints are stabilized by thick bands of tissue called ligaments. The ends of a bone that make up part of a joint are covered with cartilage to help them glide through their range of motion and decrease the friction of bone rubbing on bone.
Muscles attach to bone and have tendons that stretch across a joint. When a muscle contracts, the joint moves. Major muscle groups that affect leg movement include the buttocks, the quadriceps (in the front of the thigh), the hamstrings (in the back of the thigh), and the gastrocnemius (in the back of the calf). There are other smaller muscles, including those in the foot, that help stabilize the multiple joints in the feet.
There are two sets of blood vessels in the leg. The arterial system delivers blood, rich with oxygen, from the heart. The aorta leaves the heart and descends into the abdomen, divides into the iliac arteries and further splits into the femoral arteries at the level of the groin. The femoral artery runs along the back of the femur, and at the back of the knee (the popliteal fossa) it begins branching into smaller and smaller arteries to supply the lower leg, feet, and toes with blood.
The venous system drains blood from the leg and returns it to the heart, allowing tissue like muscle to get rid of carbon dioxide and other waste products of metabolism. There are two sets of veins in the leg, the superficial and deep venous systems. The superficial system runs along the skin while the deep system is located deep within the muscles and along the bones. Blood drains from the superficial system to the deep system through connecting veins called perforators that prevent blood clots that occur on the surface from entering the deep vein system. The superficial and deep systems come together in the groin to form the femoral vein.
Nerves from the spinal cord supply information to the leg, transmitting signals from the brain that allow purposeful movement. They also return information or sensations to the brain. These include the sensations of pain, light touch, pressure, temperature, and position. As well, nerve impulses can flow from the legs to the spinal cord and back without going up into the brain. These nerve loops allow the health care professional to test deep tendon reflexes (when the knee or ankle are tapped with a hammer) to assess spinal cord function.
Illness and injury can affect any of these structures, causing inflammation, discomfort, and pain. More than one mechanism as a cause of the leg pain may occur at the same time. Some examples include the following:
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