This study aims to investigate whether Get Back is more effective than standard rehabilitation in increasing the number of steps per day, improving physical activity levels, and functional ability for patients undergoing surgery for lumbar spinal stenosis (LSS). LSS is common, especially among older adults, leading to increased health risks and reduced quality of life. Despite its prevalence (about 60% of all spinal surgeries in Sweden), many LSS patients remain physically inactive post-surgery, worsening their health. Rehabilitation remains a global challenge with unequal access, and many patients feel disengaged from the process. Get Back is a digital rehabilitation program including three components: gradually increasing physical activity, managing fear and avoidance behaviors, and using behavior change techniques. It has shown promising results in a pilot study, increasing daily steps. The program uses a person-centered approach tailored to personal needs. This multicenter randomized controlled trial will assess efficacy, process, and cost-effectiveness. It will also explore how preoperative values such as physical capacity and psychological factors predict changes in daily steps after surgery. Data will be collected via questionnaires, functional tests, and interviews, with the primary outcome being daily steps measured with motion sensors. The study will involve 252 patients from four spinal clinics. Get Back promotes increased physical activity and accessible rehabilitation, contributing to better health for LSS patients.