Inspection of the shoulder requires that the shoulder be exposed and the patient appropriately draped. The shoulder "joint" actually consists of four different joints: sternoclavicular, acromioclavicular, glenohumeral, and scapulothoracic. Three of the joints are true joints, while the scapulothoracic joint is not a true articulating joint lined with cartilage. It is important to visualize each of the joints. Begin by inspecting the normal bony prominences and muscle bulk. The most obvious changes can be seen in the acromioclavicular joint. Comparison to the other shoulder is essential.
Palpation can be done either from in front of the patient or from behind the patient. Begin by palpating from the sternoclavicular joint along the clavicle to the acromioclavicular joint. Palpate the coracoid process and the coracoclavicular ligament. Move laterally, and palpate the tendon of the long head of the biceps. Continue palpation medially to the lesser tuberosity and laterally to the greater tuberosity. Next, palpate the scapula along the acromion and medially along the spine of the scapula. Find the superior and inferior angles of the scapula.
The muscles should also be palpated for tender points and evaluation of their bulk. The supraspinatus, infraspinatus, and teres minor can be palpated by bringing the upper limb into extension at the shoulder and palpating anteriorly (3).
Range of Motion
The motion of the joints should be observed. Watch the different joints and their symmetry of motion. This should be done from in front of and behind the patient.
The shoulder has the greatest range of motion of any joint. Subtle changes must be assessed and asymmetries noted during the physical examination. Active and passive motions should be assessed. To begin, check the patient's active range of motion. There are six directions of motion: abduction, adduction, extension, flexion, internal rotation, and external rotation. Active abduction should allow the patient to touch the dorsal surface of his hands with the arms straight above the head. Adduction will allow the patient to bring her arm into the plane of the torso. Each of these can be tested in conjunction with the testing for internal and external rotations or alone. Functional internal rotation can be demonstrated by having the patient touch his midback (Fig. 2-2). Record the level that the thumb touches, and repeat on the opposite side. Have the patient reach over the head and touch the upper back to test external rotation. As with internal rotation, record both sides. Finally, have the patient bring the straight upper limb forward to test flexion and backward to test extension.
FIGURE 2-2. Internal rotation determination during shoulder range of motion evaluation.
The shoulder should then be checked for passive range of motion. The importance of checking the passive range can be seen in a patient with adhesive capsulitis. Although there may appear to be both internal and external rotations, the motion often comes from the scapular thoracic joint. By isolating the glenohumeral motion, both can be assessed, and there is increased reliability in the assessment of the glenohumeral motion (8).
FIGURE 2-3. Stabilization of the scapula during shoulder range of motion evaluation.
Passive internal and external rotations can be tested by bringing the shoulder into 90 degrees of abduction while holding the elbow to 90 degrees of flexion. Stabilizing the scapula with one hand to truly evaluate glenohumeral motion, internally and externally rotate the shoulder (Fig. 2-3). For some examiners, placing the patient in the supine position with a posteriorly directed force on the coracoid process might be easier and has been found to be reliable (9). Note the motion, compare it to the other side, and repeat with the scapula free to see the scapulothoracic motion. Table 2-4 shows the normal range of motion.
Motor testing of the shoulder should follow the examination of the range of motion. Each motion should be tested for strength. The major muscles used to move the shoulder are the deltoid, pectoralis major, latissimus dorsi, biceps, and triceps. In addition, there are smaller stabilizing muscles, including the rotator cuff muscles. Additionally, the scapular position and control are coordinated by the trapezius, levator scapulae, rhomboids, and serratus anterior. Test the major movers with one hand stabilizing the shoulder and the other providing resistance.
After testing the larger movers of the shoulder, it is important that the smaller stabilizers are addressed, as these are often involved in the pathology of the shoulder. The supraspinatus is tested with the upper limb abducted 90 degrees, internally rotated with the thumb down and in the plane of the scapula. Apply steady pressure while asking the patient to abduct the limb (Fig. 2-4). Next, the external rotators can be assessed. Have the patient adduct the limb and flex the elbow at 90 degrees. The examiner stabilizes the elbow against the torso with one hand and places the other hand on the distal forearm. The patient then rotates the forearm away from the body against resistance.
FIGURE 2-4. Supraspinatus strength determination during shoulder evaluation.
Finally, the subscapularis should be assessed.This is the most difficult to check for subtle changes. The classically described maneuver is the "lift-off test." This is done by the patient placing the dorsum of his hand on his back while the elbow is flexed at 90 degrees. The examiner then holds the hand off the back and instructs the patient to hold his hand in that position once the hand is released. If the patient is able to maintain the hand position, the subscapularis is intact. If the hand falls to the back, there is some deficiency in the muscle (Fig. 2-5).
FIGURE 2-5. Subscapularis strength determination during shoulder evaluation.
Sensory testing of the shoulder should be done in conjunction with the neck. Of importance for the shoulder, the dermatome for the axillary nerve should be tested. This is a silver dollar-sized area over the deltoid on the lateral upper arm. This is especially important after dislocations, as the axillary nerve can be injured.
There are many tests for impingement of the rotator cuff muscles. We will address two of the more common tests. The first is the Hawkins' maneuver (10). With the arm abducted to 90 degrees, elbow flexed at 90 degrees, and the humerus in the plane of the scapula, the examiner stabilizes the scapula and internally rotates the shoulder (Fig. 2-6). Pain with this maneuver is caused by impingement of the greater tuberosity on the coracoacromial ligament.
FIGURE 2-6. Hawkins' maneuver to evaluate shoulder rotator cuff impingement.
The Neer's impingement sign is performed by stabilizing the scapula and slowly forward flexing the shoulder (11; Fig. 2-7). The elbow should be straight during the maneuver. The limb can be tested both internally rotated and neutral during testing.
FIGURE 2-7. Neer's impingement sign to evaluate shoulder rotator cuff impingement.
Another test of importance to the shoulder exam is the active compression test. The test is used to assess for anterior labral tears and acromioclavicular injuries. With the patient standing, the examiner stands on the affected side. The shoulder is brought into 90 degrees of abduction, 10 to 15 degrees of adduction, and internal rotation of the upper limb. The patient then resists a downward force by the examiner. At this point, the patient should either feel pain at the top of the shoulder (A-C joint pathology) or inside the shoulder (anterior labrum). The limb is then brought into full external rotation and the symptoms should be alleviated. Sensitivity and specificity are both excellent for the test (12).
Shoulder instability can be diagnosed with a variety of maneuvers and most likely more accurately using the results of two or more tests. The examiner can begin with the apprehension test. The patient is placed in a supine position with the upper limb to be examined next to the edge of the table. The shoulder is then abducted to 90 degrees, and the elbow is flexed. The examiner then externally rotates the shoulder (Fig. 2-8). A patient with a positive "apprehension sign" has discomfort and a feeling of apprehension in the shoulder as it is externally rotated past 90 degrees that is relieved when the examiner stabilizes the shoulder with a posteriorly directed force to the shoulder with his free hand. The second part of the examination is named the "relocation sign" (Fig. 2-9). Both parts of the examination check for anterior instability of the shoulder, although the relocation test adds specificity to the diagnosis.
FIGURE 2-8. Apprehension sign to evaluate anterior instability of the shoulder.
FIGURE 2-9. Relocation sign to evaluate anterior instability of the shoulder.
The next tests are the anterior and posterior drawer signs (13). With the patient in the same supine position, the examiner stabilizes the forearm and the humerus. Next, the examiner places her free hand on the glenohumeral joint. With the distal portion of the joint stabilized, the humerus is directed anteriorly and posteriorly (Fig. 2-10). The amount that the humeral head moves beyond the rim of the glenoid fossa is graded in Table 2-5. Similarly, this can be applied to the posterior movement.
FIGURE 2-10. Anterior and posterior drawer signs to evaluate posterior instability of the shoulder.
The final piece of instability is the inferior drawer or "sulcus sign." With the patient seated or standing, the examiner pulls down the upper limb. The examiner's free hand is stabilizing the scapula. A positive "sulcus sign" is when an indentation in the skin is noticed between the acromion and the humeral head (14).
Identifying the biomechanical flaws in a thrower that contribute to the development of bicipital tendonitis or a superior labrum anterior posterior (SLAP) lesion, or the flaws in a runner that lead to patellofemoral pain, requires an understanding muscle kinesiology and joint biomechanics. This helps determine not only the factors that may have been causative but also those that may increase the risk of an injury, and if so identified, allow prevention. This can be especially valuable during preparticipation examinations (15). The focus of sports medicine continues to be treatment rather than prevention. One reason for this is the limited scientific data that clearly demonstrate the effectiveness of prevention programs based on preinjury evaluations. Intuitively we believe that restrictions in motion or certain strength deficits may predispose an athlete to an injury, and if we address them, we can lower the risk. But do we have the research to back this up?
Much of our understanding of muscle kinesiology comes from work done in labs using electromyography (EMG) to look at muscle firing patterns. One must be extremely cautious interpreting these studies. Although very general muscle firing patterns can be determined, some important technical factors are often overlooked. The relative activity of one muscle cannot be compared with another for several reasons. One is that the amplitude of a muscle's EMG signal varies widely based on whether a muscle is contracting concentrically or eccentrically. During certain sports activities, there will usually be muscles undergoing both (usually agonists and antagonists) types of contractions simultaneously, and it may not always be readily evident which is doing which. For example, during the acceleration phase of throwing, the shoulder flexes forward, but the exact point at which the shoulder internally rotates is important in determining which of the rotator cuff muscles are contracting concentrically and which are contracting eccentrically. To be certain, one must also perform a video kinematic analysis.
Several other factors play an important role in comparing the EMG signal of different muscles. The amplitude of the EMG signal will vary based on the location of the electrode (in relation to the muscle's motor point), the type of electrode (surface vs. intramuscular), and the degree of muscle fatigue. Furthermore, because one compares the EMG activity to activity during maximal voluntary contraction (MVC) of the same muscle, activity determined during MVC must be reliable and statistically reproducible. This issue is frequently not fully and adequately addressed.
Nevertheless, the information collected on muscle kinesiology has allowed us to better understand basic muscle mechanics. Understanding the major technical limitations will help prevent us from drawing erroneous conclusions.
Biomechanics of the Overhead Athlete
The biomechanics of the overhead athlete have been extensively studied. The motion of throwing a baseball and serving a tennis ball overhead has similarly been broken into five phases: windup, early cocking, late cocking, acceleration, and follow-through. The stage of late cocking, during which the shoulder is abducted and externally rotated, may potentially be dangerous to the glenohumeral joint, where inherent instability may lead to anterior translation and load the labrum or capsule anteriorly. Symptoms of posterior impingement can also be elicited when there is excessive anterior/posterior translation compressing redundant scar tissue in the region of the posterior capsule. Kinesiological studies have demonstrated that all four muscles of the cuff are most active from the late cocking to acceleration phase (16-18). This is not surprising because the cuff is felt to be a dynamic stabilizer of the glenohumeral joint, and the position in late cocking puts the glenohumeral joint in a potentially unstable position. Studies have also demonstrated that the triceps begins to fire in late cocking and then in acceleration (16,17). This is probably to prevent hyperflexion of the elbow during late cocking and may also serve as a prestretch to create a plyometric type of contraction of the triceps during acceleration to propel the forearm, wrist, and hand along with either the racquet or the baseball. The biceps then fires during the deceleration phase to allow elbow extension to occur in a controlled fashion. If this occurs too rapidly because of inadequate biceps control, overload can occur to the biceps muscle or biceps tendon or lead to avulsion, in which the biceps tendon anchors itself along the superior labrum. Injury to the labrum at this level has been identified as a SLAP lesion (19). The muscle kinesiological data collected have supported the theoretical basis for the mechanisms of injury to these various structures. This information can then be used on physical examination so that the clinician can reproduce symptoms in the phase where injury occurs. One then combines some basic physical examination findings based on observation and palpation with functional tests, such as the apprehension sign or testing the biceps during an eccentric load. Not only can an anatomic diagnosis be made of the injured structure, but a functional diagnosis can be made as well. One must also be careful to not confuse strength with motor skill. Adequate strength on manual muscle testing does not guarantee proper muscle function. Poorly developed muscle skill, proprioception, the proper agonist/antagonist balance during contractions, and the lack of proper timing of muscle firing can all contribute to an overuse injury. Any of these should be considered at least a potentially contributing factor.
To further shed light on a more complete biomechanical picture, the kinetic chain must also be considered. This requires a sound understanding of the role each component of the chain plays during a skilled athletic maneuver. Any pathology at any point in the chain can alter the athlete's mechanics and lead to overload elsewhere. This may sound somewhat vague and generalized, but it is part of the functional approach practitioners working with athletes should consider. Throwers who have lost trunk/spine flexion/extension or pelvic/hip rotation may lose power from the loss of torque normally created during late cocking into acceleration phase or may have difficulty slowing down elbow extension during deceleration phase (20). Other components of the kinetic chain essential to minimizing trauma to the shoulder and arm are adequate neck rotation and eccentric strength of quadriceps. Compensation for restrictions in motion and relative weakness may lead to greater demands on power generated by the rotator cuff. This can create greater torque in the glenohumeral joint or require a greater and excessive eccentric contraction of the biceps. Eccentric overload of the biceps may injure the bicipital tendon of the labrum at its point of origin creating a SLAP lesion (19).