The major pain source of rotator cuff-related shoulder pain: A narrative review on current evidence

Background: Rotator cuff-related shoulder pain (RCRSP) was proposed to have a complex pain mechanism, but the exact aetiology is still unclear. A recent review summarised the updated research to analyse the traditional concept of shoulder impingement which may not be accurate. Current studies have demonstrated that mechanical factors including a reduction in subacromial space, scapular dyskinesia and different acromial shapes are unlikely directly contributing to RCRSP. Aims: Since the precise RCRSP pain mechanism remains unclear, the aim of this narrative review is to discuss possible sources of pain contributing to RCRSP according to the mechanisms-based pain classifications. Results and Discussion: Research findings on potential mechanical nociceptive factors of RCRSP are conflicting; investigations of neuropathic and central pain mechanisms of RCRSP are limited and inconclusive. Overall, available evidence has indicated moderate to strong correlations between RCRSP and chemical nociceptive sources of pain. Conclusion: Results from current research may provide new directions for future studies on the aetiology of RCRSP and its clinical management towards a biochemical view instead of the traditional mechanical hypothesis.