If the scapula fails to properly elevate the acromion, impingement may occur during the cocking and acceleration phase of an overhead activity. The two muscles most commonly inhibited during this first part of an overhead motion are the serratus anterior and the lower trapezius. These two muscles act as a force couple within the glenohumeral joint to properly elevate the acromion process, and if a muscle imbalance exists, shoulder impingement may develop. The scapula may also be misplaced if a rib deep to it is not moving correctly. Often in the case of Shoulder impingement syndrome, the scapula may be anteverted such that the shoulder on the affected side appears protracted. The ribs that may cause such an anteversion of the scapula include ribs 2–8. Diagnosis
Impingement syndrome can be diagnosed by a targeted medical history and physical examination, but it has also been argued that at least medical imaging (generally X-ray initially) and/or response to local anesthetic injection is necessary for workup. On physical exam, the physician may twist or elevate the patients arm to test for reproducible pain (the Neer sign and Hawkins-Kennedy test). These tests help localize the pathology to the rotator cuff; however, they are not specific for impingement. Neer sign may also be seen with subacromial bursitis. Response to local anesthetic
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".
While impressive, the lifestyle-modification arm of that same trial demonstrated a 58% reduction. See also
Chlorpropamide


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