​Hyperexcitability of the central nervous system, or central sensitization, is considered to be a maladaptive type of neuroplasticity often seen in patients with chronic pain. Central sensitization is frequently seen in patients with osteoarthritis, fibromyalgia, whiplash, neuropathic pain and chronic fatigue syndrome. Up to recently, shoulder pain was considered to be a pure ‘local’ problem. Tissues that are frequently linked to shoulder pain include (rotator cuff) muscles, ligaments, subacromial bursa and joint capsules. Also a body of scientific work was dedicated to unravel the movement dysfunctions in patients with shoulder pain. All these efforts have been valuable especially in terms of identification of maladaptive movement dysfunctions, but not all of them turned out to be (closely) related to shoulder pain (severity). Maladaptive neuroplasticity was not considered to be a valuable explanation for shoulder pain, not even for patients with chronic shoulder pain. 

Now 10 original research articles examining the possible role of central sensitization in shoulder pain patients are available. Different aspects of central sensitization were established in a variety of patients with unilateral shoulder pain, including subacromial impingement syndrome. The majority of the studies provides emerging evidence for the presence of central sensitization in unilateral shoulder pain (including those diagnosed of subacromial impingement syndrome). Taken into account the risk of bias of the studies, it was concluded that hypersensitivity of the central nervous system plays a role in a subgroup within the shoulder pain population. 

Further reading & references:

http://www.sciencedirect.com/science/article/pii/S0049017214002765

Jo Nijs  

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