Roughly, the volume and power of the subscapularis muscle is sufficient to oppose the volume and power of the infraspinatus and teres minor muscles posteriorly Fig. Coraco-acromial arch overhanging the head of the humerus. Observe that the acromion is broad, flat and massive; the oval clavicular facet faces obliquely upward; and the triangular coraco-acromial ligament extends from the horizontal portion of the coracoid process to the tip of the acromion lateral to the clavicular facet.
Lippincott Company, [ 4 ]. The infraspinatus muscle takes origin from the infraspinous fossa on the posterior aspect of the scapula, and its tendon together with the fibrous capsule inserts into the greater tuberosity.
It is intimately associated both structurally and functionally with the teres minor muscle. It is innervated by the suprascapular nerve Fig.
The teres minor muscle takes origin from the axillary border of the scapula, and its tendon together with the capsule inserts into the inferior facet of the greater tuberosity.
Like those of the subscapularis muscle, some of its fibers insert directly into the humerus distal to its tendinous insertion. This muscle is innervated by a branch of the axillary nerve. The supraspinatus muscle takes origin in the supraspinous fossa, and after its tendon fuses with the capsular fibers, it inserts into the greater tuberosity just posterior to the bicipital groove Fig.
At this point it should be noted that the supraspinatus, infraspinatus and teres minor muscles at their points of insertion cannot be separated into anatomic units. However, between the supraspinatus and subscapularis there is a definite interval which is occupied by the coracohumeral ligament. Also, through this interval the biceps tendon together with its synovial covering passes through the joint capsule.
The supraspinatus muscle is innervated by the suprascapular nerve. The fibrous capsule is a loose, redundant structure twice the surface area of the humeral head. On all sides except the inferior portion the fibrous capsule is strengthened by the broad, flat tendons of the rotator muscles. Where the cuff is absent inferiorly the capsule is very lax, and with the arm at the side it falls into folds which are obliterated when the arm is brought into the elevated position.
This weak point of the capsule is significant because it permits the head of the humerus to be displaced downward during normal elevation of the arm Fig.
Frontal section of the right shoulder joint, posterior view. Observe the redundancy of the capsule on the inferior aspect of the neck of the humerus. The fibrous capsule is lined with synovial membrane which is prolonged around the tendon of the long head of the biceps muscle as far as the surgical neck of the humerus, providing a synovial cover for the osseofibrous bicipital tunnel. It then ends as a blind sac and is reflected upon the tendon. Redrawn from S. The coraco-acromial arch is formed by the coraco-acromial ligament which is a strong triangular structure stretching from the coracoid process to the acromion Fig.
It arises with a wide base from the outer edge of the coracoid and tapers to a narrow band to insert into the inner border of the acromion just in front of the acromioclavicular joint. Subdeltoid region of the left shoulder. Observe the coracohumeral ligament extending from the outer border of the horizontal limb of the coracoid process to both tuberosities bridging the intertubercular sulcus; also the triangular coraco-acromial ligament and the compactness of the rotator muscles which fuse with the fibrous capsule forming the musculotendinous cuff before they insert into the superior portion of the anatomic neck of the humerus.
Note that the lower fibers of the subscapularis muscle anteriorly and the infraspinatus muscle and the teres minor posteriorly insert directly into the shaft of the humerus. From DePalma, Surgery of the Shoulder [ 4 ]. This arch is intimately related to the structures below it. It, together with the head of the humerus and the rotator cuff and the subacromial bursa, is frequently referred to as the superior humeral articulation.
The subacromial bursa and the areolar tissue in this region provide the gliding mechanism. The rotator cuff, particularly its supraspinatus portion, is in close proximity to the under surface of the coraco-acromial ligament, the acromioclavicular joint and the under surface of the acromion. Between the cuff and the arch lies the subacromial bursa whose floor is adherent to the greater tuberosity and its roof to the acromion and the coraco-acromial ligament.
Variations may be noted in the subacromial bursa. It may be a single structure extending as far as the base of the coracoid or this portion may be a separate bursa often referred to as the subcoracoid bursa. Hence, it becomes apparent that the coraco-acromial arch protects the rotator cuff and tuberosities from external injuries inflicted on the top of the shoulder.
On the other hand, an upward thrust such as a fall on the elbow may force the cuff against the arch, resulting in varying degrees of injury.
Hypertrophic changes in the bursa or of the tuberosities may cause impingement of the bursal wall against the arch, thereby interfering with the smooth rhythmical elevation and descent of the arm. Degenerative abnormalities such as hypertrophic changes and spur formation on the inferior aspect of the acromioclavicular joint may be formed as the result of this trauma.
In addition, thickening of the inferior capsular tissues of this joint may traumatize the subacromial bursa or cuff during abduction of the arm, producing loss of normal function and pain. As previously noted, two bursae may be found in the subacromial region. The subcoracoid bursa may be an independent bursa; it frequently extends as far as the base of the coracoid process and downward under the short head of the biceps and the coracobrachialis muscle. Failure to appreciate this anatomic feature while exploring the rotator cuff may result in failure to visualize the subscapularis portion of the cuff and any lesion that may be located at this site.
The tendon of the long head of the biceps inserts into the supraglenoid tubercle; it leaves the joint through an exit between the superior capsule and the head of the humerus and enters the bicipital groove. The intracapsular portion of the tendon lies immediately below the coracohumeral ligament and between the supraspinatus and subscapularis muscles Fig. Its proximal insertion is in relation to the superior glenohumeral ligament. The tendon is enveloped in a synovial covering which is an outpouching of the synovial membrane of the joint into the bicipital groove.
Certain developmental variations should be noted Fig. The tendon may appear as a double structure. It may be absent. It may be lying in an extrasynovial position in a tunnel in the fibrous capsule, or it may have a mesentery of varying length. Variations also occur in the region of the bicipital groove. Meyer in described the supratubercular ridge—a ridge of bone continuous with the medial wall of the bicipital groove Fig.
Hitchcock and Bechtol found this ridge to be well developed in 8 per cent and moderately developed in 59 per cent of the specimens reviewed. It tends to displace the biceps tendon against the transverse humeral ligament. These observers also noted variations in the obliquity of the medial wall of the bicipital groove. Only 10 per cent of the specimens had a medial wall of 90 degrees. In 35 per cent it was 75 degrees; in 34 per cent it was 60 degrees; in 13 per cent it was 45 degrees. In 6 per cent it was 30 degrees, and in 2 per cent it was 15 degrees.
Shallow grooves favor displacement of the tendon, forcing it to lie on a fascial sling. Interior of right shoulder joint, posterior view; the posterior portion of the capsule has been reflected medially. Observe the arrangement of the three glenohumeral ligaments reinforcing the anterior aspect of the fibrous capsule.
They are all directed toward the superior aspect of the glenoid fossa; in this instance they all blend with the labrum glenoidale not the case in all shoulders. Note the direct communication of the subscapularis recess with the inside of the joint cavity.
It is made up of ligaments. Ligaments are soft tissue that holds bone to bone. Shoulder injuries can occur to any part of the shoulder. Louis Children's Hospital St. Sprain, strain or jam? The rotator cuff has the important jobs of stabilizing the shoulder, elevating and rotating the arm, and ensuring the head of the humerus stays securely placed in the shoulder socket.
There are four total muscles that form the rotator cuff:. The acronym SITS is often used as the name for the collection of muscles that make up the rotator cuff: supraspinatus, infraspinatus, teres minor, and subscapularis. Each rotator cuff muscle performs a specific and important function for your shoulder joint:. All four rotator cuff muscles work together to centralize your humerus bone in the shoulder joint. When you lift your arm up, your rotator cuff muscles pull the joint together, stabilizing your shoulder.
Sometimes, shoulder pain can come on for no apparent reason. Wear and tear of the rotator cuff and shoulder joint may occur due to repetitive stress and postural neglect.
When this happens, different structures around your rotator cuff may become compromised. If you have suffered an injury to your rotator cuff, you may experience pain or weakness when lifting your arm. Your rotator cuff injury may cause difficulty with basic functional activities like lifting, reaching, or sleeping. Possible injuries and problems with these four rotator cuff muscles may include:. Any of these problems around your shoulder can cause limited motion and function. But surprisingly, some people have rotator cuff tears that show up on magnetic resonance imaging MRI though they have no pain, loss of strength, or limited function.
The presence of a rotator cuff tear does not necessarily mean you will experience problems with your shoulder. There are certain motions and activities that increase your likelihood of suffering a rotator cuff injury. These include:. Normal wear and tear of the rotator cuff, as well as aging, also increase the risk of injury.
Working to maintain healthy joints, avoiding overhead and repetitive strain on your shoulders, and maintaining proper posture can help you avoid painful shoulder injuries. Depending on the severity of a rotator cuff injury, prescribed treatment can range from simple rest and immobilization to surgery. Because recovery from surgery to repair a torn rotator cuff can be slow, orthopedic surgeons tend to shy away from ordering these procedures with the exception of younger patients, those with major tears, or older patients whose jobs depend heavily on the shoulder function.
When rotator cuff problems cause shoulder pain, consider visiting your healthcare provider to have an examination and get an accurate diagnosis of your condition. You may benefit from the services of a physical therapist PT to help figure out the cause of your shoulder pain and to work on restoring normal shoulder range of motion ROM and strength.
Your PT will ask you questions about your shoulder pain and problem. They may perform special tests for your shoulder to determine what structures are causing your pain and mobility issues.
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