Why does my shoulder hurt? A review of the neuroanatomical and biochemical basis of shoulder pain

Abstract

If a patient asks 'why does my shoulder hurt?' the conversation will quickly turn to scientific theory and sometimes unsubstantiated conjecture. Frequently, the clinician becomes aware of the limits of the scientific basis of their explanation, demonstrating the incompleteness of our understanding of the nature of shoulder pain. This review takes a systematic approach to help answer fundamental questions relating to shoulder pain, with a view to providing insights into future research and novel methods for treating shoulder pain. We shall explore the roles of (1) the peripheral receptors, (2) peripheral pain processing or 'nociception', (3) the spinal cord, (4) the brain, (5) the location of receptors in the shoulder and (6) the neural anatomy of the shoulder. We also consider how these factors might contribute to the variability in the clinical presentation, the diagnosis and the treatment of shoulder pain. In this way we aim to provide an overview of the component parts of the peripheral pain detection system and central pain processing mechanisms in shoulder pain that interact to produce clinical pain.

Ultrasound-guided shoulder girdle injections are more accurate and more effective than landmark-guided injections: a systematic review and meta-analysis

“…Shoulder pain has been identified as the third most common musculoskeletal symptom following back and knee pain 1 2. Rotator cuff, proximal long head of the biceps tendon, acromioclavicular (AC) joint, and glenohumeral (GH) joint disorders are considered the main sources of pain arising from the shoulder girdle 3 4.…”

Influence of shoulder pain on muscle function: implications for the assessment and therapy of shoulder disorders

“…The lifetime prevalence of shoulder pain in the general population is as high as 67 % (Luime et al 2004(Luime et al , 2005Ryall et al 2006). The exact cause of shoulder pain is often indefinable, partly due to the vast amount of structures potentially involved (Dean et al 2013). Although current evidence Abstract Shoulder pain is often a challenging clinical phenomenon because of the potential mismatch between pathology and the perception of pain.…”

“…Modern pain neurophysiology applied to the shoulder: part I Where does pain perception around the shoulder originate? Unfortunately, this question is not easily answered, since the neuroanatomical and biochemical basis of shoulder pain is interminable and not completely understood (Dean et al 2013). To assess and treat shoulder pain, a comprehensive understanding of the way in which pain is processed is essential.…”

“…And finally, what are the clinical implications for therapy? Despite the increasing amount of research in this area, an in-depth understanding of the bidirectional clearly emphasizes an incomplete understanding of the nature of shoulder pain, clinicians often use unsubstantiated conjectures to explain to patients why their shoulder hurts (Dean et al 2013), such as presuming a specific anatomical structure to be the cause of their pain. In addition, shoulder pain is often a challenging clinical phenomenon because of the potential mismatch between pathology and the perception of pain (Gwilym et al 2011).…”

“…In the event of a shoulder trauma, injury or pathology, substances such as substance P, potassium, serotonin, bradykinin, histamine and prostaglandins (i.e., PGE 1 , PGE 2 , PGI 2 , PGD 2 ) will increase the responsiveness of nociceptive neurons to their normal input, a phenomenon known as peripheral sensitization (Dean et al 2013). These substances are released from damaged tissue cells, the primary afferents themselves, thrombocytes and immune cells (as part of the inflammatory response), and generally work by altering the ion channel function of the nociceptive afferents.…”