Rotator Cuff Injury

Primary Impingement—Rotator Cuff Disease

Primary impingement is believed to occur as a result of mechanical wear of the rotator cuff against the anteroinferior one-third of the acromion in the superhumeral space during elevation activities of the humerus. Encroachment may be the result of intrinsic or extrinsic factors.

Rotator cuff injury

Intrinsic factors

 Intrinsic factors are those that are directly associated with encroachment of the subacromial space. They include vascular changes in the rotator cuff tendons, structural variations in the acromion, hypertrophic degenerative changes of the AC joint, or other trophic changes in the coracoacromial arch or humeral head. All of these factors decrease the superhumeral space and often have to be dealt with surgically. Neer120 first suggested that in patients undergoing surgery for impingement syndrome the size and shape of the structures that make up the coracoacromial arch are related to rotator cuff impingement. In later studies, variations in the shape and thickness of the acromion were identified and classified. One such classification, based on the shape of the anteroinferior aspect of the acromion, identified three shapes: type I (flat), type II (curved), and type III (hooked). Rotator cuff pathology is often associated with type II and III, but not type I, acromial shapes.

Extrinsic factors

 Factors that result in decreased superhumeral space and repetitive trauma to the soft tissues during the elevation of the arm include posterior capsular tightness, poor neuromuscular control of the rotator cuff or scapular muscles, faulty scapulothoracic posture with muscle imbalances, or a partial or complete tear of the tissues in the superhumeral space (incurred during a traumatic or degenerative situation). Neer described three pathological stages of impingement that demonstrate the potentially progressive nature of the pathology over time . Other authors have identified chronic inflammation, possibly due to repetitive microtrauma in the joint region, as a stimulus for the development of frozen shoulder.


Neer identified tendinitis/bursitis as a stage II impingement syndrome . The following sections describe specific pathological diagnoses and presenting signs and symptoms.

Supraspinatus tendinitis

 With supraspinatus tendinitis, the lesion is usually near the musculotendinous junction, resulting in a painful arc with overhead reaching. Pain occurs with the impingement test (forced humeral elevation in the plane of the scapula while the scapula is passively stabilized so the greater tuberosity impacts against the acromion or with the arm in internal rotation while flexing the humerus).  There is pain on palpation of the tendon just inferior to the anterior aspect of the acromion when the patient’s hand is placed behind the back. It is difficult to differentiate tendinitis from subdeltoid bursitis because of the anatomical proximity.

Infraspinatus tendinitis

 With infraspinatus tendinitis, the lesion is usually near the musculotendinous junction, resulting in a painful arc with overhead or forward motions. It may present as a deceleration (eccentric) injury due to overload during repetitive or forceful throwing activities. Pain occurs with palpation of the tendon just inferior to the posterior corner of the acromion when the patient horizontally adducts and laterally rotates the humerus.

Bicipital tendinitis

 With bicipital tendinitis, the lesion involves the long tendon in the bicipital groove beneath or just distal to the transverse humeral ligament. Swelling in the bony groove is restrictive and compounds and perpetuates the problem. Pain occurs with resistance to the forearm in a supinated position while the shoulder is flexing (Speed’s sign) and on palpation of the bicipital groove. Rupture or dislocation of this humeral depressor may escalate impingement of tissues in the suprahumeral space.

Bursitis (subdeltoid or subacromial)

 When acute, the symptoms of bursitis are the same as those seen with supraspinatus tendinitis. Once the inflammation is under control, there are no symptoms with resistance.

Other Impaired Musculotendinous Tissues

The following are examples of other musculotendinous problems in the shoulder region. The pectoralis minor, short head of the biceps, and coracobrachialis are subject to microtrauma, particularly in racket sports requiring a controlled backward then a rapid forward swinging of the arm, as are the scapular stabilizers as they function to control forward motion of the scapula. The long head of the triceps and scapular stabilizers are often injured in motor vehicle accidents as the driver holds firmly to the steering wheel on impact. A fall on an outstretched hand or against the shoulder may also cause trauma to the scapular stabilizers, which, if not properly healed, continue to cause symptoms whenever using the arm or when maintaining a shoulder posture. Injury, overuse, or repetitive trauma can occur in any muscle being subjected to stress. Pain occurs when the involved muscle is placed on a stretch or when contracting against resistance. Palpating the site of the lesion causes familiar pain.

Secondary impingement—Shoulder


Secondary impingement is used to describe symptoms resulting from faulty mechanics due to hypermobility or instability of the GH joint with the increased translation of the humeral head. The instability may be multidirectional or unidirectional.

Multidirectional instability

 Some individuals have physiologically lax connective tissue causing excessive mobility in the joints of the body. In the GH joint, the humeral head translates to a greater degree than normal in all directions. Many individuals, particularly those involved in overhead throwing or lifting activities, have some inherent laxity or develop laxity of the capsule and instability from continually subjecting the joint to stretch forces.  A hypermobile joint may be satisfactorily supported by strong rotator cuff muscles; but once the muscles fatigue, poor humeral head stabilization leads to faulty humeral mechanics, trauma, and inflammation of the suprahumeral tissues. This trauma is magnified with the rapidity of control demanded in the overhead throwing action.  Similarly, in individuals with poor rotator cuff muscle strength and function, the ligaments become stressed with repetitive use and hypermobility, resulting in impingement. With instability, the impingement of tissue in the suprahumeral space is the secondary effect. Hypermobility can cause problems in addition to impingement, such as subluxation, dislocation, or rotator cuff tendinitis, which with repetitive microtrauma can lead to degenerative changes including bone spurs, tendon rupture, or capsular restrictions and frozen shoulder.

Unidirectional instability with or without impingement

Unidirectional instability (anterior, posterior, or inferior) may be the result of physiologically lax connective tissue but is usually the result of trauma and usually involves rotator cuff tears. The tears can be classified as acute, chronic, degenerative, or partial- or full-thickness tears. Often there is damage to the glenoid labrum and tearing of some of the supporting ligaments.

Traumatic tears or paralysis

 Partial-thickness tears or full avulsion of the greater tubercle may occur in the elderly as the result of falling on an outstretched arm.  In young patients, trauma is usually associated with capsular injury, with or without labrum injury, resulting in instability. Dislocation of the humerus may occur with ensuing instability. The instability can lead to progressive degeneration and eventually tears in the supporting structures. Tears are associated with pain and most commonly weakness of shoulder abduction and external rotation.

 Anterior instability usually occurs with force against the arm when it is in an abducted and externally rotated position, and it frequently involves detachment of the anterior capsule and glenoid labrum (Bankart lesion). There may also be a fractured piece or flattening of the anterior lip of the glenoid.68 Positive signs include apprehension, load and shift, and anterior drawer tests.

Posterior instability is the result of a forceful thrust against a forward-flexed humerus or fall on an outstretched arm. There is a positive posterior drawer sign.

Inferior instability is the result of rotator cuff weakness/ paralysis and is frequently seen in patients with hemiplegia. It is also prevalent in patients with multidirectional instability. This is detected with a positive sulcus  sign .

Insidious (atraumatic) onset

 Neer has identified rotator cuff tears as a stage III impingement syndrome, a condition that typically occurs in persons over age 40 after repetitive microtrauma to the rotator cuff or long head of the biceps. With aging, the distal portion of the supraspinatus tendon is particularly vulnerable to impingement or stress from overuse strain. With degenerative changes, calcification and eventual tendon rupture may occur. Chronic ischemia caused by tension on the tendon and decreased healing in the elderly are possible explanations, although Neer stated that, in his experience, 95% of tears are initiated by impingement wear rather than by impaired circulation or trauma.

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