Approximately 20% of all office visits to primary care providers involve musculoskeletal complaints. The purpose of this chapter is to survey the most common presenting complaints of the upper and lower extremities, highlighting the etiology, clinical findings, differential diagnosis, and evidence-based treatment options for each.
The term subacromial impingement defines any entity that compromises the subacromial space and irritates the enclosed rotator cuff tendons. Impingement can involve any of the structures within the subacromial space, and the term encompasses various entities from subacromial bursitis to rotator cuff calcific tendonitis and tendinosis. Often these entities arise in a similar fashion and may be difficult to differentiate.
Impingement syndrome is classified into external, internal, and secondary impingement. The most common form is external impingement, which is caused by compression of the rotator cuff tendons as they pass under the coracoacromial arch. Subacromial bursitis can develop subsequently and intensify the compression. Internal impingement is caused by fraying of the infraspinatus tendon where it contacts the posterior glenoid. This occurs while the arm is maximally abducted and externally rotated and is seen in athletes who participate in overhead and throwing activities. Lastly, secondary impingement is caused by glenohumeral instability. Diagnosis is made with a meticulous history and physical examination, and appropriate imaging.
Diagnosis of subacromial impingement is primarily clinical. The patient complains of dull shoulder pain of insidious onset over weeks to months. Less often, these symptoms arise following trauma. Pain is typically localized to the anterolateral acromion and radiates to the lateral deltoid. Pain is aggravated at night, by sleeping with the arm overhead or lying on the involved shoulder. Overhead activities, throwing motions, and activities in which the humerus is flexed with an inward rotation also exacerbate symptoms.
Physical examination usually reveals normal range of motion (ROM), although the patient may experience a painful arc of motion or pain upon approaching maximum internal rotation and forward flexion. Muscular weakness is sometimes seen in the supraspinatus muscle or the internal and external rotators of the shoulder. Supraspinatus strength (empty can test) is tested with the arm in 90 degrees of abduction and 30 degrees of forward flexion, with the thumb pointing downward. Decreased strength indicates a positive test. To differentiate weakness caused by pain from actual loss of strength, it may be necessary to perform a subacromial injection with an anesthetic to alleviate the pain variable.
Radiographs that may aid in diagnosis include anteroposterior (AP), outlet, and axillary views of the affected shoulder. Curvature of the acromion or acromial spurs can be seen on an outlet view and may contribute to compression of the rotator cuff musculature or subacromial impingement.
Provocative testing includes the ...