A lumbar microdiscectomy surgery is performed to remove the portion of a herniated disc that is irritating or inflaming the nerve root. A microdiscectomy is performed through a small incision in the midline of the low back. First, the back muscles, called erector spinae, are lifted off the bony arch, called the lamina, of the spine. Since these back muscles run vertically, they can be moved out of the way rather than cut. The surgeon is then able to enter the spine by removing a membrane over the nerve roots. This membrane is called the ligamentum flavum. Often, a small portion of the inside facet joint is removed both to facilitate access to the nerve root and to relieve pressure over the nerve. The nerve root is then gently moved to the side and the disc material is removed from under the nerve root. Only the herniated portion of the disc is removed; the healthy portion of the disc is left intact. After the piece of the disc that is irritating or inflaming the nerve root has been removed, the pressure is off the nerve immediately and it has room to heal. A herniated disc pressing on a nerve root can cause severe leg pain. While it may take weeks or months for the nerve root to fully heal and any numbness or weakness to get better, patients normally feel relief from the leg pain almost immediately after a microdiscectomy.