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The rotator cuff is a group of four muscles that hold the shoulder in place and enable the upper arm and shoulder to perform a wide range of movements. These four muscles are supraspinatus, infraspinatus, teres minor, and subscapularis. The subscapularis muscle is the largest and strongest of the four and is responsible for the internal rotation of the shoulder. The supraspinatus, infraspinatus, and teres minor muscles work together with subscapularis to stabilize the glenohumeral joint, allowing for a wide range of motion in the shoulder.
| Characteristics | Values |
|---|---|
| Muscles that rotate the humerus | Supraspinatus, Infraspinatus, Teres Minor, Subscapularis |
| Function | The rotator cuff muscles help perform all movements of the upper arm and shoulder, including flexion, abduction, internal rotation, and external rotation. |
| Anatomy | The rotator cuff muscles arise from the scapula and connect to the head of the humerus, forming a cuff around the glenohumeral joint. |
| Injuries | Rotator cuff tears, tendinitis, impingement, and degeneration are common causes of shoulder pain and may require physical therapy or surgery. |
| Treatment | Treatment for rotator cuff injuries includes conservative treatment with NSAIDs, exercises, and in severe cases, surgery. |
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What You'll Learn
- The subscapularis muscle is the main internal rotator of the shoulder
- The rotator cuff is made up of four muscles that help perform movements of the upper arm
- The supraspinatus, infraspinatus, teres minor, and subscapularis muscles are the four rotator cuff muscles
- The rotator cuff muscles are responsible for stabilising the shoulder joint
- The glenohumeral joint is a ball-and-socket joint that attaches the upper limb to the axial skeleton
The subscapularis muscle is the main internal rotator of the shoulder
The subscapularis muscle is a large and powerful triangle-shaped muscle. It is located in the subscapular fossa of the scapula, attaching between the scapula and the proximal humerus. The muscle fibres course laterally from the costal surface of the scapula, gradually narrowing towards a round tendon that connects to the proximal humerus. The subscapular bursa, which is a large bursa that communicates with the shoulder joint, separates the subscapularis tendon from the neck of the scapula. The tendon then inserts into the lesser tubercle of the humerus and the anterior part of the articular capsule of the glenohumeral joint.
The subscapularis muscle derives its name from its orientation under the scapula, with "sub" meaning under and "scapula" referring to the wing bone. The subscapularis nerve innervates the muscle, and the subscapular artery provides its blood supply. Lymph drainage flows into the axillary nodes. The subscapularis muscle also contributes to the creation of concavity compression, a stabilizing mechanism that prevents dislocation of the humerus by translating forces.
The subscapularis muscle is the only medial (internal) rotator among the rotator cuff muscles. Its unique axis of pull, from the proximal humerus to the costal scapular surface, allows the subscapularis to medially rotate the humeral head within the glenoid fossa. In addition to internal rotation, the subscapularis muscle also aids in adducting the arm, a sequence of movements observed during walking when arms swing. Along with the other rotator cuff muscles, the subscapularis muscle helps to stabilize the shoulder joint when the deltoid, pectoralis major, biceps, and triceps brachii muscles are active.
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The rotator cuff is made up of four muscles that help perform movements of the upper arm
The rotator cuff is a group of muscles and tendons that surround the shoulder joint. It is made up of four muscles: the supraspinatus, infraspinatus, subscapularis, and teres minor. These muscles work together to stabilise the shoulder joint and enable a wide range of movements in the upper arm.
The supraspinatus muscle allows you to rotate and lift your arm. It stretches from the top of the scapula (shoulder blade) to the upper end of the humerus (the head of the upper arm bone). This muscle is unique among the rotator cuff muscles in that it is not a rotator of the humerus.
The infraspinatus is a powerful lateral rotator of the humerus. It acts as a powerful rotator of the upper arm bone, enabling movements such as abduction and lateral rotation. The tendon of this muscle is sometimes separated from the capsule of the glenohumeral joint by a bursa, a fluid-filled sac that reduces friction and provides cushioning.
The subscapularis is the largest and strongest of the four rotator cuff muscles. It is responsible for internal rotation of the shoulder, allowing the arm to move towards the midline of the body. This muscle also helps to hold the arm outstretched, away from the body, and prevents the anterior dislocation of the humerus during abduction.
The teres minor assists in turning and rotating the arm. It attaches to the outside edge of the scapula and connects to the humerus beneath the infraspinatus. Together, these four muscles and their attached tendons provide stability to the shoulder joint while facilitating various arm movements.
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The supraspinatus, infraspinatus, teres minor, and subscapularis muscles are the four rotator cuff muscles
The subscapularis muscle is the largest and strongest of the four rotator cuff muscles, providing 53% of total cuff strength. It is a large triangular-shaped muscle that lies below the other three. It participates in most shoulder motions but is especially important for the rotation of the arm toward the midline of the body (medial rotation). Unlike the other three muscles, the subscapularis attaches to the front, rather than the back, of the upper arm. The subscapular bursa lies between the subscapularis tendon and the capsule, reducing frictional damage to the subscapularis muscle during internal shoulder rotation.
The supraspinatus muscle is also one of the four rotator cuff muscles. Its tendon is primarily composed of Type I collagen, with relatively small amounts of Type III collagen, decorin, and biglycan. The tendon wraps around the humerus, and its fibrocartilage portion has a collagen and proteoglycan content similar to tissues that have been subjected to compressive loads.
The infraspinatus muscle is another of the four rotator cuff muscles. Its tendon has a microstructure described as a five-layer structure. Layer one is composed of the superficial fibres of the coracohumeral ligament. Layer two, the main portion of the cuff tendons, is made up of closely packed parallel tendon fibres extending directly from the muscle bellies to the insertion on the humerus. Layer three is a thick tendinous structure with smaller fascials than layer two and a less uniform orientation. Layer four is composed of loose connective tissues with thick bands of collagen fibres running perpendicular to the primary fibre orientation of the cuff tendons.
The teres minor muscle is the final muscle of the four rotator cuff muscles. Together, these four muscles attach to the upper part of the humerus at different points, forming a cuff around the glenohumeral joint. The glenohumeral joint is a ball-and-socket joint that attaches the upper limb to the axial skeleton. It is the most mobile joint in the human body, allowing for a wide range of motion at the upper limb.
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The rotator cuff muscles are responsible for stabilising the shoulder joint
The rotator cuff is made up of four muscles: supraspinatus, infraspinatus, teres minor, and subscapularis. These muscles are responsible for stabilising the shoulder joint, allowing for a wide range of motion in the upper limb. They provide strength and stability during motion, with the subscapularis muscle being the largest and strongest, providing 53% of total cuff strength. The rotator cuff muscles are deeper muscles and are very active in the neuromuscular control of the shoulder complex during upper extremity movements.
The rotator cuff muscles arise from the scapula and connect to the head of the humerus, forming a cuff around the glenohumeral (GH) joint. The glenohumeral joint is a ball-and-socket joint that attaches the upper limb to the axial skeleton. It is the most mobile joint in the human body, allowing for a wide range of motion, including flexion, extension, abduction, adduction, and internal and external rotation. However, this mobility comes at the cost of stability, as the bony surfaces offer little support.
The rotator cuff muscles provide stability to the glenohumeral joint by compressing the humeral head against the glenoid fossa. They keep the head of the humerus within the small glenoid fossa of the scapula, enlarging the range of motion in the GH joint and avoiding mechanical obstruction during elevation. The rotator cuff tendons act as a combined and integrative structure, with a microstructure described as a five-layer structure. Layer one is composed of the superficial fibres of the coracohumeral ligament, while layer two is the main portion of the cuff tendons, extending directly from the muscle bellies to the insertion on the humerus.
Injuries to the rotator cuff are common and can result in shoulder pain, impaired function, and a reduced quality of life. These injuries can occur due to trauma, repetitive strain, or age-related degeneration. Treatment for rotator cuff injuries depends on the type of damage, with most cases responding well to conservative treatment and physical therapy. However, severe or persistent symptoms may require surgical intervention.
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The glenohumeral joint is a ball-and-socket joint that attaches the upper limb to the axial skeleton
The glenohumeral joint, also known as the shoulder joint, is a ball-and-socket joint that connects the upper limb to the axial skeleton. It is formed by the dynamic articulation between the scapula's glenoid cavity and the head of the humerus. The glenoid cavity is shallow, and its surface area is only a quarter of the size of the humeral head. This disproportionate size contributes to the joint's high mobility and susceptibility to dislocation. The glenoid cavity is deepened by a fibrocartilaginous rim called the glenoid labrum, which increases the contact area between the glenoid and the humeral head, enhancing joint stability.
The glenohumeral joint capsule is a fibrous sheath that forms a continuous support structure around the articulating elements. Within this capsule are distinct thickened bands known as the glenohumeral ligaments, which reinforce the joint capsule and prevent anterior shoulder dislocation. These ligaments become taut at varying degrees of abduction and humeral rotation, unlike traditional ligaments that carry tensile force along their length. The superior, middle, and inferior glenohumeral ligaments form a Z-shaped pattern on the capsule.
The rotator cuff muscles play a crucial role in stabilising the glenohumeral joint. They are composed of four muscles: the supraspinatus, infraspinatus, subscapularis, and teres minor. The subscapularis is the main internal rotator of the shoulder and provides 53% of total cuff strength. The rotator cuff tendons act as a combined and integrative structure, with a microstructure described as a five-layer system.
The shoulder joint also contains multiple bursae, which are small, fluid-filled sacs that reduce friction and provide cushioning between joint structures. The subacromial bursa is one of the largest bursae in the body, allowing the rotator cuff to slide easily beneath the deltoid muscle. However, it is vulnerable to injury, and dysfunction can lead to subacromial impingement syndrome and subacromial bursitis, a common source of shoulder pain.
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Frequently asked questions
The rotator cuff is made up of four muscles that hold the shoulder in place and enable the movement of the upper arm and shoulder.
The four muscles that constitute the rotator cuff are the supraspinatus, infraspinatus, teres minor, and subscapularis.
The subscapularis is the largest and strongest cuff muscle, providing 53% of total cuff strength. It is the main internal rotator of the shoulder and is especially important for the rotation of your arm toward the midline of your body (medial rotation).
The glenohumeral joint, or shoulder joint, is a ball-and-socket joint that attaches the upper limb to the axial skeleton. It is the most mobile joint in the human body, but this comes at the cost of stability.
