Patrick J. McMahon, MD; Robert E. Sallis, MD

VOL 106 / NO 7 / DECEMBER 1999 / POSTGRADUATE MEDICINE

CME learning objectives

• To become more familiar with common causes of shoulder pain
• To learn common signs of various types of shoulder injuries
• To understand when conservative therapy is appropriate and when referral is indicated

This is the first of three articles on musculoskeletal problems

Preview: A painful shoulder can present diagnostic challenges for the clinician because of the complexity of the structures involved. Fortunately, most shoulder problems seen in the primary care setting are caused by relatively few conditions. In this article, Drs McMahon and Sallis review common shoulder problems, including impingement syndrome, shoulder stiffness, glenohumeral instability, acromioclavicular joint problems, and glenohumeral osteoarthritis. In addition, they outline treatment options and provide information about when referral is needed.
McMahon PJ, Sallis RE. The painful shoulder: zeroing in on the most common causes. Postgrad Med 1999;106(7):36-49

The shoulder is a complex structure that can cause puzzling problems. Its function involves the thorax and three bones--the humerus, the glenoid, and the clavicle--plus nearly 30 muscles. In addition, four articulations (ie, acromioclavicular, sternoclavicular, glenohumeral, scapulothoracic) must move normally for the shoulder to function correctly.

To further complicate the picture, disease processes elsewhere in the body may be involved in shoulder pain, and clinical assessment should not focus solely on the shoulder. Pain can be referred to the shoulder from the hand (eg, carpal tunnel syndrome), the neck (eg, radicular symptoms), the chest (eg, cardiac pain), or the abdomen (eg, diaphragmatic irritation).

Carefully listening to the patient's concerns often provides important clues to diagnosis of shoulder problems. Although pain is a subjective symptom, detailed assessment can provide insight into its cause. The duration, anatomic location, and character of the pain should be specifically assessed. In addition, information about the patient's use of analgesics and the presence of pain at night can be helpful. Symptoms of shoulder instability should be sought out by specifically asking if the shoulder feels like it slips out or if it has ever dislocated.

Understanding the temporal relationship to sports activity and the postural relationship to arm motion is also helpful in determining shoulder problems. The onset of night pain, especially when the patient is lying on the affected side, may indicate a rotator cuff tear. Pain during overhead activities may be a sign of impingement syndrome. Shoulder stiffness and weakness may be important for diagnosis, and mechanical problems in the shoulder, such as catching or locking, may indicate a labrum tear. Finally, details about how the injury affects activities of daily living and sports performance can provide helpful clues to identify the problem.

Physical examination

Physical examination of the shoulder consists of several parts, including visual inspection, palpation, range-of-motion testing, strength testing, neurovascular assessment, and general physical evaluation.

Visual inspection includes examining the skin and the contour of the entire shoulder girdle. Special attention should be given to areas of swelling or muscle atrophy. Side-to-side differences should be recorded, with the understanding that some mild differences are normal between the dominant and nondominant shoulders. For example, if the patient is a baseball player, the musculature is often hypertrophied, and the scapula may be displaced slightly inferior in the throwing arm.

Palpation should be performed from the neck to the fingers on all aspects of the upper extremities. Specific areas that should be palpated for tenderness include the sternoclavicular joint, clavicle, acromioclavicular joint, anterior and posterior glenohumeral joint lines, biceps tendon, subacromial space, and scapula. Both active and passive motion of the shoulder should be assessed.

With a rotator cuff tear, the patient has full passive but reduced active range of motion. By comparison, severe impingement or capsulitis reduces both active and passive range of motion. The rotator cuff muscles should also be tested for weakness (indicative of a rotator cuff tear) or pain (indicative of tendinitis). Motion should always be compared with the contralateral shoulder.

Brown and coworkers (1) found that major league pitchers have different ranges of motion for each shoulder. In the pitching arm, with the shoulder in abduction, there are 11° less extension, 15° less internal rotation, and 9° more external rotation. Therefore, comparison with the contralateral arm should be done with this variance in mind (2).

Diagnostic signs and tests
Among the various signs of impingement, the Neer impingement sign is the most reliable. To elicit this sign, the patient's shoulder is rotated internally, and his or her arm is brought passively into forward flexion. The sign is positive if pain is elicited in the mid arc of motion (figure 1: not shown). The best signs for anterior shoulder instability are the apprehension and the relocation signs (3). With the patient supine and muscles relaxed, the shoulder is abducted to 90° and then gently rotated externally to the limit of motion. In this "apprehension" position, the patient may be afraid that the joint will dislocate, which is recognized as a positive apprehension sign. In patients with more subtle instability, however, this maneuver produces posterosuperior glenohumeral joint pain as the tuberosity or the rotator cuff impinges against the posterosuperior glenoid rim (4). When a gentle, anteriorly directed force is applied to the humeral head, the sign becomes more obvious (figure 2: not shown).

The relocation test is done with the patient in the same position as during the apprehension test, except that a posteriorly directed force is applied to the humeral head (figure 3: not shown). This force relocates the joint so that, in a patient with anterior instability, the apprehension and pain resolve. Continuous maximal external rotation is applied throughout the test, and usually external rotation of the shoulder can be increased while the posteriorly directed force is applied. This test is useful in differentiating anterior instability from primary impingement.

Imaging studies
In patients with persistent pain, shoulder radiographs should be obtained to detect calcification in the capsule or supraspinatus tendon, which is suggestive of tendinitis. An outlet view in those patients with chronic impingement may show a hooked (type III) acromion. An axillary radiographic examination should be done in patients who have a history of shoulder instability.

Magnetic resonance imaging (MRI), computed tomography, and other imaging studies can be used to reinforce the physical findings in difficult cases. They can also be helpful in a few special circumstances, such as when a rotator cuff abnormality is suspected but the history and physical examination yield contradictory findings. MRI is especially helpful for subtle rotator cuff tears. However, routine use of imaging studies is not cost-effective for most patients with shoulder problems.

Impingement syndrome

Impingement syndrome comprises a spectrum of conditions, including shoulder bursitis, rotator cuff tendinitis, and rotator cuff tears. Each of these conditions has a similar cause and presentation. The end stage of impingement syndrome is a rotator cuff tear.

Shoulder bursitis
The shoulder, or subacromial, bursa is located in the subacromial space, which is under the acromion and above the rotator cuff. Inflammation of the shoulder bursa typically causes an achy shoulder pain that becomes worse with activity. Patients often report that pain radiates into the biceps area in the front of the upper arm. Sometimes the pain in this area is more severe than that in the shoulder itself.

Shoulder bursitis pain intensifies with overhead movement of the affected arm, but the patient might not volunteer this information unless specifically asked. Sports activities, such as throwing a baseball or playing tennis or golf, sometimes trigger the pain, but more often physical labor, such as painting a ceiling or lifting heavy items to high shelving, brings on bursitis pain.

Most patients with shoulder bursitis are quite comfortable when the affected arm is at their side, and many have tried and received some relief from anti-inflammatory medications. Bursitis pain is generally mild to moderate in intensity. It is usually only when the shoulder problem persists for several months without improving that patients consult a physician.

On physical examination, routine passive and active ranges of shoulder motion usually are normal. However, it is important to ask the patient to elevate the arm in forward flexion in the sagittal plane and in abduction in the coronal plane. The patient should also be able to externally rotate the arm at his or her side with the elbow flexed to 90°. Lastly, the patient is asked to reach as far up the midline of the back as possible. This test helps determine internal rotation. (Most people can reach to about the tenth thoracic vertebra.) Strength is normal for each of these motions in patients with shoulder bursitis, but pain may occur with resistance testing. Eliciting pain with a Neer impingement sign usually confirms the diagnosis, and injection of 10 mL of lidocaine into the subacromial space (Neer impingement test) results in almost complete resolution of pain.

The initial treatment of shoulder bursitis includes application of ice, rest from painful activity, and use of nonsteroidal anti-inflammatory drugs (NSAIDs). Range-of-motion and rotator cuff strengthening exercises should begin as pain allows. Specifically, rotator cuff strengthening should include internal and external rotation with the affected arm at the side (figures 4 and 5: not shown). An elastic cord that can be tied to a doorknob (Theraband) can be helpful in performing these exercises. If this treatment fails to relieve the pain, a corticosteroid injection in the subacromial space is often efficacious. Referral to an orthopedic surgeon is appropriate if the patient does not improve after 3 months of treatment. Such patients may need subacromial decompression to relieve impingement in the subacromial space.

Rotator cuff tendinitis
Rotator cuff tendinitis is simply a more severe form of shoulder bursitis. It is more often seen in middle-aged or older patients with chronic shoulder pain than in younger people. Anatomically, the subacromial bursa is directly superior to the supraspinatus tendon of the rotator cuff. Over time, inflammation of the bursa also involves this tendon. Patients with rotator cuff tendinitis often have pain that is more severe than that caused by shoulder bursitis. The achy character of the pain is similar to that with bursitis, and patients tend to hold the affected arm at their side. Tendinitis pain usually persists for 3 to 4 months and, like bursitis pain, it worsens with overhead activity and may awaken the patient at night.

On physical examination, the patient may be unable to actively move the shoulder through a full range of motion. This effect is most pronounced in abduction, forward flexion, and internal rotation. As in shoulder bursitis, the Neer impingement sign is positive, as is the Neer impingement test. Also of note, the patient is able to move the arm actively through a full range of motion once lidocaine hydrochloride is injected into the subacromial space.

Performing the Neer impingement test (subacromial injection of lidocaine) in a patient with rotator cuff tendinitis is one of the most satisfying aspects of caring for shoulder problems. The patient is positively delighted when the pain is relieved and gains considerable confidence that the shoulder problem can be alleviated.

As in shoulder bursitis, treatment includes rest, application of ice, and use of NSAIDs. As the pain recedes, range-of-motion and rotator cuff exercises are prescribed. A steroid injection may be given if needed. Referral to an orthopedic surgeon is appropriate if no response is seen after 3 months of treatment.

Rotator cuff tear
Rotator cuff tear is the end stage on the impingement syndrome spectrum and is more painful than the most severe form of rotator cuff tendinitis. In fact, because most rotator cuff tears are small, patients with such tears often have a history of rotator cuff tendinitis. It was once believed that all patients with rotator cuff tears required surgery, but this is no longer the case. With a small rotator cuff tear, the other shoulder muscles often compensate and symptoms resolve. Only patients with medium to large rotator cuff tears have the three characteristic signs of a rotator cuff tear: pain, weakness, and a decrease in active range of motion. Pain tends to be severe and often awakens the patient at night.

The pain triggered by overhead movement of the affected arm is often so severe in patients with rotator cuff tears that they either refrain from this type of activity or simply cannot raise the arm. Despite this decrease in active range of motion, passive range of motion is normal, and the examiner can move the arm with no problems. As in shoulder bursitis and rotator cuff tendinitis, the Neer impingement sign is usually positive. However, in a rotator cuff tear, the Neer impingement test results in only partial relief of the pain.

Treatment for rotator cuff tear depends on whether or not the patient can actively elevate the arm through a full range of motion against gravity. The patient's age, general health, occupation, and lifestyle should also be considered. If the patient can lift the arm, treatment can proceed as with shoulder bursitis and rotator cuff tendinitis. However, if treatment is ineffective after 3 months, referral to an orthopedic surgeon should be considered. Also, in patients who cannot lift the arm against gravity, surgical repair is usually indicated. Physical therapy involving passive range-of-motion exercises is important both before and after surgery to ensure that the shoulder remains supple.

Shoulder stiffness

Shoulder stiffness can be related to a number of conditions, including frozen shoulder and adhesive capsulitis. It is most often seen in older patients whose shoulders are immobilized after an injury. The stiffness may occur after minimal trauma and seems to be more common in diabetic patients than in the general population. The patient usually has achy pain similar to that with impingement syndrome. Unlike patients with large rotator cuff tears, who have decreased active but normal passive range of motion, patients with shoulder stiffness have decreases in both active and passive ranges of motion.

Treatment includes use of NSAIDs plus physical therapy aimed at strengthening the rotator cuff and gently increasing the range of motion. Corticosteroid injections into both the glenohumeral joint and subacromial space may be helpful. Patients should be told that shoulder stiffness can be caused by a number of shoulder problems and that most patients recover with simple treatment, though the treatment course is long and sometimes frustrating. Symptoms often get worse and then stabilize before they improve. Unfortunately, each of these phases can last 6 to 9 months. In the end, most patients regain about 80% of normal motion.

Patients who have seriously limited shoulder motion should be referred to an orthopedic surgeon. Surgical intervention, such as shoulder manipulation under anesthesia or arthroscopic capsular release, may speed recovery in some cases.

Shoulder dislocation and instability

Most shoulder dislocations occur when the humeral head moves anterior and inferior to the glenoid. After an acute anterior shoulder dislocation, the arm is fixed in a position of adduction and internal rotation. Sometimes patients can reduce the dislocation by themselves, but a trip to the emergency department often is necessary.

Once the joint is relocated, the patient usually recovers in a couple of weeks. Symptoms disappear except when the shoulder is in abduction and external rotation--the apprehension position. With the shoulder in this position, which is similar to that when the arm is cocked in preparation for throwing a ball, the patient feels considerable pain and is afraid the shoulder will "go out" again.

On physical examination, range of motion and strength are normal and the Neer impingement sign is negative. However, when the patient is supine and the arm is in abduction and external rotation, there is considerable apprehension that the shoulder will dislocate (a positive apprehension sign). This test must be done carefully to prevent dislocation of the shoulder joint. The relocation sign is also positive in these patients.

Treatment of anterior shoulder instability includes rest, which may include use of a sling for 4 weeks in patients with dislocation, application of ice, and an aggressive physical therapy program to regain rotator cuff strength. If the symptoms have not been relieved within 3 to 6 months, surgical repair may be necessary. It is important to note that recurrent instability correlates more closely with age than with any other factor. Patients less than 25 years old at the time of the initial episode have a recurrence rate that ranges from 60% to 90%. On the other hand, patients more than 45 years old have a recurrence rate of less than 15%. Early surgical intervention should be considered in young athletes who suffer one or more shoulder dislocations.

Glenohumeral arthritis

Glenohumeral arthritis is a less common cause of shoulder pain and stiffness than the previously discussed conditions. The signs and symptoms are similar to those of shoulder stiffness, and achy shoulder pain often awakens these patients at night. Both active and passive ranges of motion are decreased. Crepitus is often palpable at the joint.

Treatment includes rest, application of ice, and use of NSAIDs, along with gentle rotator cuff strengthening exercises. A corticosteroid injection into the subacromial space or into the glenohumeral joint may also be helpful. Although radiographs may show evidence of advanced osteoarthritis, many patients do very well with this treatment program over a prolonged period of time. Unlike the situation with osteoarthritis of the weight-bearing joints, joint replacement surgery is rarely necessary with glenohumeral arthritis.

Acromioclavicular joint problems

The most common acromioclavicular joint problems are shoulder separation and osteoarthritis.

Shoulder separation
Instability of the acromioclavicular joint, or shoulder separation, is a common injury. It typically results from a fall onto the acromion, the "point of the shoulder," which drives the acromion inferiorly, separating it from its articulation with the distal end of the clavicle. This injury results in stretching or tearing of the ligaments binding the clavicle to the acromion and the coracoid process.

Shoulder separation is classified into three different types. In a type I injury, the acromioclavicular ligaments are sprained. Although the patient has pain on palpation of the joint, the radiographic examination is normal compared with the contralateral shoulder. Treatment includes rest, application of ice, and use of NSAIDs, followed by gentle active range-of-motion exercises as pain allows. Symptoms usually resolve after about a month, and splinting is rarely necessary.

In type II injuries, the acromioclavicular ligaments are torn. The injured tissues are tender, and the distal end of the clavicle is more prominent on the affected side than on the contralateral side. Radiographs show that the distal clavicle is slightly higher than the acromion. Initial treatment involves either a figure-eight shoulder device or an arm sling for comfort, along with use of ice and NSAIDs. Range-of-motion exercises should begin as soon as the patient can tolerate them.

With type III injury, both the acromioclavicular and the coracoclavicular ligaments are completely disrupted. The distal clavicle is very prominent and tender and on radiographic evaluation can be seen resting completely above its articulation with the acromion. Referral to an orthopedic surgeon is needed only for patients engaged in physical labor that necessitates overhead activity. In others, treatment similar to that for the type II injury is efficacious. Despite the cosmetic deformity, patients regain full function and can even participate in overhead sports activities, such as baseball, football, and tennis, without difficulty. In those few patients whose symptoms persist after conservative treatment, late surgical reconstruction usually leads to a good outcome.

Acromioclavicular joint osteoarthritis
Arthritis of the acromioclavicular joint may occur after an acromioclavicular separation or as the result of excessive weight training, especially bench pressing exercises. These patients have achy shoulder pain that is worse with activity and localized to the top of the shoulder. The pain also is exacerbated by motion of the arm across the body more than by overhead movements. On physical examination, the patient has normal range of motion, normal strength, and a negative Neer impingement sign. Palpation of the acromioclavicular joint causes pain, as does the "crossover test" (horizontal adduction). Radiographs show osteoarthritis of the joint.

Treatment consists of anti-inflammatory medications and gentle active range-of-motion exercises. If symptoms persist after 3 months of treatment, referral to an orthopedic surgeon is indicated. Corticosteroid injection into the joint may relieve symptoms, but resection of a small amount of the distal clavicle often is needed. After surgery, patients regain full function and can even participate in overhead activities, such as baseball, football, and tennis, without difficulty.

Fracture

Shoulder fractures are complex and beyond the scope of this article, but a few comments are warranted. The most serious complication of shoulder fracture is shoulder stiffness. Therefore, range-of-motion exercises should be started early after the fracture to prevent impairment. Pendulum exercises (ie, active motion of the shoulder with the arm hanging at the side) can begin as early as 1 week after the fracture.

Active-assist range-of-motion exercises under the direction of a physical therapist can begin when tolerated, usually at 3 to 4 weeks after the injury. A device that holds the arm rigidly against the abdomen (eg, shoulder immobilizer splint) is seldom necessary. A sling allows some range of motion of the shoulder as the patient moves and therefore is less likely to result in shoulder stiffness. The sling is for comfort only and can be discontinued as the pain diminishes.

Summary

Most shoulder problems seen by the primary care physician involve impingement syndrome or problems at the acromioclavicular joint. Despite the complexity of the structures involved, most of these conditions can be diagnosed and treated without difficulty. MRI or other imaging studies are seldom needed but can be used to confirm a questionable diagnosis. Referral to an orthopedic surgeon is appropriate if shoulder problems persist for 3 to 6 months or if there is evidence of a medium or large rotator cuff tear, severe shoulder stiffness, or a complicated fracture.

References

1. Brown LP, Niehues SL, Harrah A, et al. Upper extremity range of motion and isokinetic strength of the internal and external rotators in major league baseball players. Am J Sports Med 1988;16(6):577-85
2. McFarland EG, Campbell G, McDowell J. Posterior shoulder laxity in asymptomatic athletes. Am J Sports Med 1996;24(4):468-71
3. Jobe F, Giangarra CE, Kvitne RJ, et al. Anterior capsulolabral reconstruction of the shoulder in athletes in overhand sports. Am J Sports Med 1991;19(5):428-34
4. Davidson PA, Elattache NS, Jobe CM, et al. Rotator cuff and posterior-superior glenoid labrum injury associated with increased glenohumeral motion: a new site of impingement. J Shoulder Elbow Surg 1995;4(5):382-90

Dr McMahon is assistant professor, department of orthopedic surgery, University of Pittsburgh School of Medicine. He was formerly assistant professor, department of orthopedic surgery, University of California, Irvine, College of Medicine. Dr Sallis is on the staff of the department of family medicine, Kaiser Permanente Medical Center, Fontana, California, and is assistant clinical professor of family medicine, University of California, Riverside, Biomedical Sciences Program. Correspondence: Patrick J. McMahon, MD, Department of Orthopedic Surgery, University of Pittsburgh School of Medicine, 4601 Baum Blvd, Pittsburgh, PA 15213.