Shoulder pain is usually caused by problems local to the shoulder
joint or the supporting or adjacent structures. However, the shoulder
is a site of referred pain from serious conditions such as myocardial
infarction or diaphragmatic irritation from intra-abdominal bleeding
or hollow viscus perforation.
This chapter details disorders of the shoulder joint and structures
deep to the joint. For a discussion of cardiac and intra-abdominal
disorders that may present with shoulder pain, the reader is referred
to Section 7, Cardiovascular Disease, and Section 9, Gastrointestinal
The most common causes of nontraumatic shoulder pain, in descending order
of frequency, are rotator cuff tendinopathy, impingement, acromioclavicular
joint disease, adhesive capsulitis, and referred pain.1 After neck
and back pain, shoulder pain is the most common type of musculoskeletal
pain, accounting for approximately 16% of all musculoskeletal complaints.2,3 The
sex- and age-standardized incidence of chronic shoulder pain is
approximately 9.5 per 1000 [95% CI (7.9 to 11.2
per 1000)].3 Disability from shoulder
disease ranks in severity with that from conditions such as congestive
cardiac failure, acute myocardial infarction, diabetes mellitus,
and clinical depression.3
Overuse can produce pathologic changes in the rotator cuff structures that
progress along a continuum starting with subacromial bursitis from mechanical
irritation, progressing to rotator cuff tendinitis, and eventually
leading to partial- and full-thickness rotator cuff tears. Laborers
who work with their arms above the horizontal and athletes of all
ages, especially throwers, swimmers, and racquet sports enthusiasts,
are the most susceptible to chronic overuse injuries.
Conditions affecting other intrinsic structures of the shoulder
complex can also cause pain. In addition, extrinsic disorders can
refer pain to the shoulder and must be considered in the differential
diagnosis. A focused history and physical examination carried out
with an understanding of the complex anatomy and function of the
shoulder is essential in determining the source of shoulder pain.
Establishing the proper diagnosis, initiating the appropriate treatment,
and making timely referrals for follow-up are critical in preserving
the function and mobility of the shoulder.
The shoulder is designed for mobility in all directional planes,
rather than for stability. Its functions are to help position the
hand and upper extremity for accurate and efficient use, and to
provide strength and power to upper extremity movements. To meet
the many demands placed on it, the shoulder uses three bones, four
joints, and a specialized set of soft tissues consisting of muscles,
tendons, ligaments, and bursae.
The humerus, clavicle, and scapula make up the bony structures
of the shoulder complex. The scapula is the most complex bone and
consists of the body and three bony extensions: the glenoid, the
coracoid, and the acromion.
The four joints of the shoulder are the glenohumeral, acromioclavicular, sternoclavicular,
and scapulothoracic. The glenohumeral joint is a ball-and-socket
joint and is the central axis of shoulder motion. ...