This cross-sectional study compared 3D scapular kinematics, shoulder ROM, muscle force, and resting posture between 45 patients with subacromial impingement syndrome and 45 age- and sex-matched controls. It asks which physical factors actually differentiate impingement patients from healthy individuals. Findings challenge assumptions about the primacy of scapular dyskinesia and poor posture in this syndrome.
The dominant clinical teaching around shoulder impingement often focuses on scapular dyskinesia and poor posture as central modifiable factors. This study tests that assumption directly in a matched cohort, and the results complicate the narrative.
The most robust findings are the force and ROM deficits: impingement patients were weaker in every direction and stiffer in every plane tested. These are the targets that rehabilitation should prioritize — strengthening (especially rotator cuff external rotation and scapular plane elevation) and restoring flexibility.
The scapular kinematic differences, while statistically present, were small (under 5 degrees) and inconsistent with prior studies showing opposite trends. The authors suggest this reflects measurement variability, heterogeneous patient populations, and the real possibility that only a subset of impingement patients have true scapular dyskinesia. Treating all impingement patients as if they have scapular dysfunction misses this nuance.
Resting posture showed no difference between groups at all. This does not mean thoracic mobility is irrelevant. The authors cite evidence that dynamic thoracic mobility during arm elevation may matter more than static posture. But it does mean that correcting posture as the primary intervention lacks support from this data.
This cross-sectional study compared 3D scapular kinematics, shoulder ROM, muscle force, and resting posture between 45 patients with subacromial impingement syndrome and 45 age- and sex-matched controls. It asks which physical factors actually differentiate impingement patients from healthy individuals. Findings challenge assumptions about the primacy of scapular dyskinesia and poor posture in this syndrome.
The dominant clinical teaching around shoulder impingement often focuses on scapular dyskinesia and poor posture as central modifiable factors. This study tests that assumption directly in a matched cohort, and the results complicate the narrative.
The most robust findings are the force and ROM deficits: impingement patients were weaker in every direction and stiffer in every plane tested. These are the targets that rehabilitation should prioritize — strengthening (especially rotator cuff external rotation and scapular plane elevation) and restoring flexibility.
The scapular kinematic differences, while statistically present, were small (under 5 degrees) and inconsistent with prior studies showing opposite trends. The authors suggest this reflects measurement variability, heterogeneous patient populations, and the real possibility that only a subset of impingement patients have true scapular dyskinesia. Treating all impingement patients as if they have scapular dysfunction misses this nuance.
Resting posture showed no difference between groups at all. This does not mean thoracic mobility is irrelevant. The authors cite evidence that dynamic thoracic mobility during arm elevation may matter more than static posture. But it does mean that correcting posture as the primary intervention lacks support from this data.