Background: Patients with lumbar spinal stenosis may complain of poor balance, decreased physical function and problems maintaining physical activity levels due to radiculopathy. Decompressive surgery is often indicated if conservative management fails to achieve a satisfactory clinical outcome. While surgical management has proven effective at treating radiculopathy, and patients report increased physical function post-operatively, objective measures of postural control and physical activity remains sparse. This study aims to investigate the effects of decompressive surgery on balance and activity levels of elderly patients with lumbar spinal stenosis using objective measurements. Methods and analysis: This is a 24 month, multi-centre, prospective cohort study. Patients at or above 65 years of age with MRI-verified symptomatic lumbar spinal stenosis will be recruited from two separate inclusion centres, and all participants will undergo decompressive surgery for lumbar spinal stenosis. Preoperative data is collected up to 3 months before surgery, with follow-up data collected at 3, 6, 12 and 24 months postoperatively. Balance measurements are performed using the Wii Balance Board, mini Balance Evaluation Systems Test and Tandem test, and data concerning physical activity levels are collected using ActiGraph wGT3XBT accelerometers. Patient reported outcomes regarding quality of life and physical function are collected from the EuroQol5D, 36 Item Short Form Health Survey and Zurich Claudication Questionnaire. Primary outcomes are the change in sway area of centre of pressure and total activity counts per day from baseline to follow-up at 24 months. A sample size of 80 participants has been calculated. Ethics and dissemination The study has been approved by the Regional Ethics Committee of Region Zealand (ID EMN202208110) and the Danish Data Protection Agency (ID REG1002022). All results from the study will be published in international peer reviewed journals and presented at national and international conferences. Study findings will be disseminated through national patient associations. Trial registration number: NCT06075862 & NCT06057428

The authors have declared no competing interest.

This work is supported by the Dept. of Orthopaedic Surgery at Zealand University Hospital Koge, Denmark, the cross-regional fund of Region Zealand and Region of Southern Denmark, and A.V. Lykfeldts og Hustrus Legat. OZ has received a travel grant of 8,000 DKK from the Guildal Foundation. As of writing, no other specific grants have been received from public, commercial or not-for-profit sectors.

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

The Regional Ethics Committee of Region Zealand gave ethical approval of this work (case ID EMN-2022-08110)

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I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

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I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

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All data produced in the present study will be available upon reasonable request to the authors.