Overcoming Subacromial Impingement, as a Term and Concept: Rationale and Proposals

Background/Objectives: Subacromial impingement syndrome has traditionally been described as pathological contact between the rotator cuff and the anterolateral aspect of the acromion and has long been regarded as a primary cause of shoulder pain and tendon injury. Despite a substantial body of literature questioning the very existence of subacromial impingement as a pathological entity, the diagnosis continues to be widely used in medical and rehabilitation settings as a predominantly biomechanical explanation for shoulder pain. The objective of this review is to determine whether the concept of subacromial impingement should be abandoned in clinical practice, interprofessional communication, and the clinician-patient relationship, and to explore which alternatives may be more appropriate. Methods: This narrative review is based on an appraisal of the most relevant literature on this topic published in recent years using scientific databases. Results: Evidence suggests that narrowing of the subacromial space is a consequence of rotator cuff muscle-tendon unit incompetence rather than its cause. Furthermore, such dysfunction appears to arise primarily from degenerative rather than compressive mechanisms. Advances in shoulder biokinematics have also challenged the validity of the clinical 'special tests' traditionally used to support the diagnosis, as these tests do not appear to accurately identify the presumed target structures. Moreover, surgical decompression of the subacromial space has not proved to be more effective than conservative treatment when performed as a standalone procedure, and it often provides no additional benefit when combined with rotator cuff repair in terms of reducing re-tear rates. Nevertheless, it may still have a role as an adjunctive procedure to improve exposure of the surgical site or in selected cases. Discussion: An inaccurate biomechanical explanation may lead patients to believe that arm elevation is inherently harmful, thereby resulting in disability and increased pain. It may also encourage the selection of invasive treatments over conservative management, despite current international guidelines recommending conservative treatment as the first-line approach for subacromial shoulder pain. Indeed, such an approach has been shown to be effective in a substantial proportion of patients, with lower costs and risks, less time away from work, and the advantage that it does not preclude surgery if subsequently required. Conclusions: The concept of subacromial impingement appears to be flawed, as the biomechanical mechanism on which it is based is not supported by current evidence. This concept should therefore be reconsidered in clinical practice because of its potential nocebo effects on patients and its capacity to divert clinicians from more appropriate clinical assessment and management strategies. Accordingly, this review proposes alternative terminology and conceptual frameworks better aligned with current evidence and contemporary approaches to the assessment and management of subacromial shoulder pain.