Sciatica is formed as a result of irritation of the nervus spinalis. The cause of such can be deformation of bone structures, and constriction of the sciatic nerve. As a result of irritation, a painful sensation arises, which can lead to lumpy and overextended muscles, the formation of nodules in the muscles and problems with nutrition of the skin. The nerve, under the influence of certain factors, ceases to function normally, which can cause chills or fever in the limb, increased pallor of the skin and a sharp change in its color. These changes already indicate the appearance of sciatica, and also ensure its progression, increasing pain.