Introduction Patients with subacromial pain syndrome (SAPS) are typically referred to physiotherapy as first line of treatment. Only half of patients get a satisfactory treatment outcome from this. Acromial morphology, poor scapular control, and impingement are pathophysiological factors associated with SAPS. These are expressed varyingly in SAPS-patients, and could be associated to treatment outcome. The aim was to investigate if acromial morphology, scapular control, and ultrasonographic impingement were associated with outcome from 3-months of treatment, in SAPS-patients.

Materials and Methods Patients were referred to 3-months physiotherapy. Acromial morphology, scapular control and ultrasonographic impingement were analyzed, through multiple linear regression, for an association to change in SPADI before and after treatment. Potential confounders were addressed in the analyses.

Results 69 patients were included in the analysis for scapular control, 62 patients for ultrasonographic impingement, and 45 patients for acromial morphology. Acromial morphology was associated with poorer treatment outcome in both the adjusted and unadjusted model. The final model predicted a change in SPADI of 1.8 points per degree of increased acromial curve (more hook-shaped acromion). There was no association between scapular control or ultrasonographic impingement to change in SPADI.

Conclusion Acromial morphology was associated to the outcome after physiotherapy, with increasing acromial curve associated to poorer SPADI-scores. Ultrasonographic impingement and scapular control were not associated to treatment outcome. The exact relationship between acromial morphology and non-surgical treatment outcome needs to be explored further to confirm findings and determine the clinical implications.