Sudden sciatica may be due to the following reasons: First, it may be a sudden protrusion of the intervertebral disc caused by various reasons. The protruding disc compresses the nerve root, causing edema and inflammation of the nerve root, which in turn causes sciatica. Second, it may be the sudden onset of spinal stenosis, lumbar spondylolisthesis and these diseases, which can also cause disc protrusion or vertebral instability, stimulating the nerve roots and causing sciatica. Third, it may be pear-shaped muscle syndrome, pear-shaped muscle syndrome also refers to the thickening, enlargement, thickening of the pear-shaped muscle, compression of the sciatic nerve, when the condition suddenly aggravates one day, the symptoms suddenly appear. Fourth, it may be a tumor of the muscles around the sciatic nerve or the sciatic nerve, causing nerve damage suddenly appear, appearing sciatic nerve sudden pain. Fifth, it may be sciatica or damage to the spinal cord, or it may be a sudden onset of sciatica because of the pain that occurs in a short period of time. There are more specific causes, and they have to be ruled out one by one according to different situations.