Lumbar spinal stenosis (LSS) is one of the most common degenerative diseases of the spinal column, with symptoms including low back pain which worsens with ambulation, poor balance, decreased activity due to pain, and a marked decrease in quality of life (QoL). Prevalence rises with age, and current treatment options range from varied conservative management strategies, to surgical intervention with decompression of neural structures. While the effects of surgical decompression on back pain and QoL has been widely researched, the effects of surgery on activity levels is less well understood. Though patients generally have subjective improvements in this parameter after surgery, objective measurements in this patient group have been lacking. This study aims to investigate the effects of decompressive surgery on activity levels in elderly patients with LSS. Measurements of activity will be taken before and after decompressive surgery, as well as with regular intervals during a two-year follow-up period. A better understanding of the effect that LSS has on activity may lead to more patients being able to receive surgical treatment, which is hypothesized to lead to an increase in QoL and less perceived disability amongst this patient group.