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".
It not only supports the diagnosis for impingement syndrome, but it is also therapeutic. Imaging
Plain x-rays of the shoulder can be used to detect some joint pathology and variations in the bones, including acromioclavicular arthritis, variations in the acromion, and calcification. However, x-rays do not allow visualization of soft tissue and thus hold a low diagnostic value. Ultrasonography, arthrography and MRI can be used to detect rotator cuff muscle pathology. MRI is the best imaging test prior to arthroscopic surgery. Due to lack of understanding of the pathoaetiology, and lack of diagnostic accuracy in the assessment process by many physicians, several opinions are recommended before intervention. Treatment
Impingement syndrome is usually treated conservatively, but sometimes it is treated with arthroscopic surgery or open surgery. Conservative treatment includes rest, cessation of painful activity, and physical therapy. Physical therapy treatments would typically focus at maintaining range of movement, improving posture, strengthening shoulder muscles, and reduction of pain. NSAIDs and ice packs may be used for pain relief.Therapeutic exercises might be favorable intervention compared to passive treatment approaches, electrotherapy and placebo. 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. Exercises may help to regain the scapulo-humeral rhythm and scapular control which may reduce pain.