Introduction Partnership between patients and healthcare professionals can improve physical functioning and activities of daily living. For patients with lumbar spinal stenosis (LSS), the cardinal symptom is neurogenetic claudication limiting walking ability. After surgical treatment most patients stay inactive. Rehabilitation may improve postoperative outcome, thus the person-centered 12-week rehabilitation program Get Back was designed to facilitate increased physical activity. The aim of this study was to evaluate the fidelity of partnership in Get Back. Methods Twelve inactive patients with LSS scheduled for surgery participated in Get Back guided by two physiotherapists. After completion all patients were asked via questionnaire if they felt involved throughout their rehabilitation. Semi-structured interviews were conducted with all patients regarding their experiences of participating in Get Back. After each treatment session the physiotherapists logged if they had used the three routines of partnership (initiating, working and safeguarding). We used descriptive statistics to analyze quantitative data. Interviews were analyzed qualitatively using deductive content analysis with a predetermined categorization matrix comprising the three routines of partnership.  Finally, with convergent mixed methods-design, quantitative and qualitative results were merged. Results All patients answered “yes” to perceived self-participation throughout the rehabilitation and the physiotherapists reported high usage of the three routines of partnership. These quantitative results concurred with the qualitative results, in which the patients expressed experiences of initiating, working and safeguarding the partnership. However, the patients did not perceive that the health plan was used to plan or document activities; instead, they referred to the activity diary and verbal feedback from the physiotherapists. This may contrast with the physiotherapists’ logged use of the health plan. Conclusions The results of our study support that a high degree of partnership was present during Get Back. However, there is a need to clarify and facilitate the use of the health plan.