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The labelling of non-traumatic shoulder pain related to the structures of the subacromial space has been debated for many years. Historically, labelling of shoulder diagnoses and exploring theories about the underlying causes of shoulder pain are interrelated. Many authors use the phrase ‘syndrome’ describing a combination of findings, often occurring together, with an unknown or heterogeneous underlying pathogenesis. As such, Dr Charles Neer introduced the diagnostic label of ‘subacromial impingement syndrome’ (SIS) of the shoulder in 1972. This label was based on the mechanism of structural impingement of the structures of the subacromial space. This concept has been the dominant theory of injury to the rotator cuff tendons and other structures in the subacromial space, and has served as the rationale for clinical tests, surgical procedures and rehabilitation protocols.
Controversy about the label ‘SIS’
However, the label of SIS is now controversial, as recent evidence suggests that this concept does not fully explain the mechanism.1–3 Until a few years ago, SIS was a widely accepted ‘umbrella’ term for a number of possible underlying structural or biomechanical causes. Throughout the years, the description progressed from SIS to ‘impingement related shoulder pain’, with the growing opinion that ‘impingement’ represents a cluster of symptoms and a possible mechanism for the pain, rather than a pathoanatomic diagnose itself. The …