It has been posited that the shoulder forward position (as demonstrated in the far-right image), is implicated in subacromial impingement, however new evidence suggests that perhaps this is not the case.
Nxt Gen PT Evidence: While it has been suggested that dysfunctional posture of the scapula, thoracic spine, and cervical spine is associated with the development of subacromial impingement syndrome (SIS), what does the evidence tell us? Well a recent narrative review performed by Nxt Gen Adjunct Faculty, Dr. Adam Rufa, found a lack of strong evidence to support an association between posture and SIS. The evidence examining this association is plagued by poorly defined diagnostic criteria, wide sample variation, and poor statistical power.
Clinical Implications: While many of us focus on assessment and correction of posture in patients with SIS, evidence for a relationship is quite poor. Focusing on reducing pain, and progressing with movements important to that patient, is potentially a more plausible progression of treatment.
Better Your Practice: You can probably focus less on posture when treating patients with confirmed SIS. That stated, there are many things we can do such as understanding that patients symptoms, and how they move, and intervene accordingly.
Rufa A. Subacromial Impingement and Posture. Phys Therapy Reviews. 2014; 19: 338-351.