The pain has been described as dull rather than sharp, and lingers for long periods of time, making it hard to fall asleep.

[2] Weight training exercises where the arms are elevated above shoulder height but in an internally rotated position such as the upright row have been suggested as a cause of subacromial impingement.

[8] It is a wide, flat bone lying on the posterior thoracic wall that provides an attachment for three different groups of muscles.

[9] These muscles attach to the surface of the scapula and are responsible for the internal and external rotation of the glenohumeral joint, along with humeral abduction.

One action the scapula performs during a throwing or serving motion is elevation of the acromion process in order to avoid impingement of the rotator cuff tendons.

[8] If the scapula fails to properly elevate the acromion, impingement may occur during the cocking and acceleration phase of an overhead activity.

[17] The physician may inject lidocaine (usually combined with a steroid) into the bursa, and if there is an improved range of motion and decrease in pain, this is considered a positive "Impingement Test".

Physical therapy treatments would typically focus at maintaining range of movement, improving posture, strengthening shoulder muscles, and reduction of pain.

A recent meta-analysis done on rotator cuff tendinopathy has shown that nearly all types of active resistance training programs were proven to be effective in improving pain and shoulder function with no significant differences among the different exercise types, further cementing the favorability of a more active intervention over passive modalities when it comes to rotator cuff issues.

The impinging structures may be removed in surgery, and the subacromial space may be widened by resection of the distal clavicle and excision of osteophytes on the under-surface of the acromioclavicular joint.

A 2019 review found that the evidence does not support decompression surgery in those with more than 3 months of shoulder pain without a history of trauma.

[24] A recent metaanalysis has further supported that early SIS would likely benefit from non-operative treatment modalities and surgical open decompression should be considered only with chronic presentation.

[4][25] In 1972, Charles Neer proposed that impingement was due to the anterior third of the acromion and the coracoacromial ligament and suggested surgery should be focused on these areas.

[26][27] Second, a computerized three-dimensional study failed to support impingement by any portion of the acromion on the rotator cuff tendons in different shoulder positions.

[35] And finally, there is growing evidence that routine acromioplasty may not be required for successful rotator cuff repair, which would be an unexpected finding if acromial shape had a major role in generating tendon lesions.

[36] In summary, despite being a popular theory, the bulk of evidence suggest that subacromial impingement probably does not play a dominant role in many cases of rotator cuff disease.