The NORDSTEN Studies/The Observational Cohort Study

Inclusion Criteria: * Presence of clinical symptoms of spinal stenosis. Neurogenic claudication or radiating pain to one or both lower limbs * Radiological findings corresponding to the clinical symptoms of LSS. Central stenosis or lateral recess stenosis with or without degenerative spondylolisthesis * Able to understand Norwegian language, both spoken and written * Able to give informed consent and to answer the questionnaires * Over 18 years of age Exclusion Criteria: * Not willing to give written consent * Participation in other clinical trial that may interfere with this trial * American Society of Anesthesiologists (ASA) 4 or 5 * Age older than 80 years * Not able to comply fully with the protocol, including treatment, follow-up or study procedures (psychosocially, mentally and physically) * Presence of cauda equina syndrome (bowel and bladder dysfunction) or complete motor deficit * Presence of an isthmic defect in pars interarticularis * Former fracture of the thoracolumbar region * Previous surgery in the lumbar region * Distinct symptoms in one or both legs due to other diseases, e.g. polyneuropathy, vascular claudication or osteoarthritis * Lumbosacral scoliosis of more than 20 degrees verified on standing x-ray AP-view