Aims. The purpose of this study was to investigate the prevalence of sarcopenia and to examine its impact on patients with degenerative lumbar spinal stenosis (DLSS). Patients and Methods. This case-control study included two groups: one group consisting of patients with DLSS and a second group of control subjects without low back or neck pain and related leg pain. Five control cases were randomly selected and matched by age and gender (n = 77 cases and n = 385 controls) for each DLSS case. Appendicular muscle mass, hand-grip strength, sit-to-stand test, timed up and go (TUG) test, and clinical outcomes, including the Oswestry Disability Index (ODI) scores and the EuroQol EQ-5D were compared between the two groups. Results. The prevalence of sarcopenia, as defined by hand-grip strength, was significantly higher in the DLSS group (24%) when compared with the age- and gender-matched control group (12%) (p = 0.004). In the DLSS group, the sarcopenia subgroup demonstrated inferior results for the TUG test and ODI scores when compared with the non-sarcopenia subgroup (p = 0.006 and p = 0.039, respectively) after adjusting for age and gender. Conclusion. This study demonstrated a higher prevalence of sarcopenia in patients with DLSS and highlighted its negative effect on clinical outcomes. Cite this article: Bone Joint J 2016;98-B:1093–8