While most people think of joint disease or injury, muscle, tendon, and ligament strain, or back or leg nerve irritation as the most common causes of leg pan venous insufficiency can also be a common culprit.  Venous insufficiency stems from damage to the valves and the walls of the veins itself. Veins are very elastic (to assist in storing the blood until the heart is ready to pump it) and have special valves that prevent the blood from flowing backwards. When the valves or the vein walls are damaged, blood can pool in the extremities; this almost exclusively occurs in the legs due to the added effect of gravity pulling blood away from the heart. It is characterized by swelling, burning, itching, or skin color changes of the legs. Those affected may also notice their legs feel heavy, tired, restless, or achy.