Endoscopic rhizotomy is a procedure performed on patients suffering from chronic low back pain caused by inflammation or osteoarthritis of the lumbar facet joints. In people over the age of 40, this is the most common cause of chronic low back pain. Pain is typically provoked by getting up in the morning, after long sitting or when standing for a long time. Facet joints are true joints on the posterior side of the spine and are innervated by small branches of the spinal nerves, the so-called medial branches. Each joint is innervated by the medial branch from the level above and the one from below. As these little nerves do not have any other function than sending information from the joints to the brain, their destruction by locally applied heat is a well studied and effective intervention since the 1970s. A conventional radiofrequency procedure is performed using needles and x-ray guidance. Its disadvantage is that there is no real visual control. This is the big advantage of a full-endoscopic approach. The procedure is performed with the patient in the prone position. Local or general anaesthesia is possible. The painful joints are marked on the skin and usually only one 1cm incision is made. A small working tube is carefully inserted and the endoscope is advanced to the medial branch, which lies on the outside of the spine. Under direct control of the endoscope, the medial branch at each level is identified and coagulated or cut with a flexible thermal probe. This procedure is repeated at each painful joint, most commonly the joint L4/5 and L5/S1 or L3/4 on one side.