Sciatica refers to pain radiating along the sciatic nerve, which originates in the lower spine as a combination of several nerves from the low back region. The nerve branches from the spine to the left and right buttocks and then travels down the back of the legs, at about the middle of the thighs, to the feet.
By definition, sciatica is tenderness and pain radiating along the sciatic nerve, typically showing up on one side of the body. There are two sciatic nerves—one for each leg. These are the longest nerves in the human body. Each originates from several nerve roots that exit from the spinal cord, then thread through your sacrum and merge to form the main body of the sciatic nerve. The sciatic nerve passes between layers of the deep buttock muscles (gluteus medius and gluteus maximus), through the deep muscles of the back of the thigh, and down to the outer edge of your leg to your foot.