This will identify impingement of the rotator cuff but is also sensitive for subacromial bursitis.Irritation or entrapment of the lower subscapular nerve, which innervates the subscapularis and teres major muscles, will produce muscle guarding at the shoulder that will restrict motion into external rotation, abduction, or flexion. The aforementioned tests will assist in diagnosing bursitis over other conditions. The diagnosis of impingement syndrome should be viewed with caution  in people who are less than forty years old, because such individuals may have subtle glenohumeral instability. Imaging
X-rays may help visualize bone spurs, acromial anatomy and arthritis. Further, calcification in the subacromial space and rotator cuff may be revealed. Osteoarthritis of the acromioclavicular (AC) joint may co-exist and is usually demonstrated on radiographs.MRI imagining can reveal fluid accumulation in the bursa and assess adjacent structures. In chronic cases caused by impingement tendinosis and tears in the rotator cuff may be revealed. At US, an abnormal bursa may show

fluid distension,
synovial proliferation, and/or
thickening of the bursal walls.In any case, the magnitude of pathological findings does not correlate with the magnitude of the symptoms. Special considerations
In patients with bursitis who have rheumatoid arthritis, short term improvements are not taken as a sign of resolution and may require long term treatment to ensure recurrence is minimized. Joint contracture of the shoulder has also been found to be at a higher incidence in type two diabetics, which may lead to frozen shoulder (Donatelli, 2004).
Subacromial bursitis is a condition caused by inflammation of the bursa that separates the superior surface of the supraspinatus tendon (one of the four tendons of the rotator cuff) from the overlying coraco-acromial ligament, acromion, and coracoid (the acromial arch) and from the deep surface of the deltoid muscle. The subacromial bursa helps the motion of the supraspinatus tendon of the rotator cuff in activities such as overhead work. Musculoskeletal complaints are one of the most common reasons for primary care office visits, and rotator cuff disorders are the most common source of shoulder pain.Primary inflammation of the subacromial bursa is relatively rare and may arise from autoimmune inflammatory conditions such as rheumatoid arthritis, crystal deposition disorders such as gout or pseudogout, calcific loose bodies, and infection. More commonly, subacromial bursitis arises as a result of complex factors, thought to cause shoulder impingement symptoms. These factors are broadly classified as intrinsic (intratendinous) or extrinsic (extratendinous). They are further divided into primary or secondary causes of impingement. Secondary causes are thought to be part of another process such as shoulder instability or nerve injury.In 1983 Neer described three stages of impingement syndrome. He noted that "the symptoms and physical signs in all three stages of impingement are almost identical, including the impingement sign..., arc of pain, crepitus, and varying weakness". The Neer classification did not distinguish between partial-thickness and full-thickness rotator cuff tears in stage III.