Lumbar Spinal Stenosis (LSS) is a clinical entity were narrowing of the spinal canal gives a compression of the the neural and vascular structures in the spinal canal. This often gives neurogenic claudication and sometimes severe Low Back Pain (LBP). Surgery for LSS is today the most often performed procedure in the adult lumbar spine. Beneficial effect of surgical treatment is well documented by several clinical trials, and a Cochrane review article from 2005 concludes that surgical treatment is superior to non-surgical treatment. The surgical solution is to decompress the stenotic part of the lumbar spine. There is no consensus in the literature of which surgical method that gives best long term clinical results. The investigators are therefore planning a Randomized Controlled Trial, where they will compare clinical and radiological results of three different surgical methods for LSS. The main outcome of this study is to answer which surgical method that gives the best long term clinical results. And, secondary outcome is to find out how much increase of the Dural Sac Cross Sectional Area is needed to give a long time relief of the patients` symptoms.