Dominic Stone
The subscapularis muscle is a large, powerful, triangle-shaped muscle that fills the subscapular fossa of the scapula (wing bone). It is one of the four muscles that make up the rotator cuff apparatus, along with the supraspinatus, infraspinatus, and teres minor muscles. The subscapularis is the largest and strongest of these muscles, and its primary function is internal rotation, although it also aids in adduction and extension of the humerus. The subscapularis muscle plays an important role in shoulder movement and stability, and injuries to this muscle can result in pain and weakness in the shoulder and upper arm.
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What You'll Learn
The subscapularis is the largest and strongest muscle of the rotator cuff
The subscapularis muscle is a large and powerful triangular-shaped muscle that fills the subscapular fossa of the scapula. The name subscapularis is derived from its location under the scapula, or wing bone. It is the largest and strongest muscle of the rotator cuff, which is composed of four muscles in total, the other three being the supraspinatus, infraspinatus, and teres minor muscles. The subscapularis is located at the anterior surface of the scapula and originates at the subscapular fossa, specifically the medial and lower two-thirds of the groove on the lateral border.
The muscle fibres transition into a tendon, which inserts onto the lesser tubercle of the humerus and the anterior part of the shoulder joint capsule. The subscapularis is the only muscle of the rotator cuff with the function of internally rotating the humerus. In certain positions, it can also aid in adduction and extension. This function helps prevent anterior displacement of the humerus. The arm's position can affect the actions caused by this muscle. For example, when the arm is raised, the subscapularis pulls the humerus forward and downward.
The subscapularis is an essential stabiliser of the shoulder joint, contributing to the fixation of the proximal humerus during movements of the elbow, wrist, and hand. It also plays a role in the stabilisation and steering of the humeral head within the glenoid cavity during various movements of the upper limb. The subscapularis is supplied by the upper and lower subscapular nerves (C5-C6), which are branches of the posterior cord of the brachial plexus. The primary blood supply to the subscapularis muscle is the subscapular artery, a branch of the axillary artery.
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It originates at the subscapular fossa
The subscapularis muscle is a large, powerful, triangle-shaped muscle that fills the subscapular fossa. The term "subscapularis" comes from its orientation under the scapula, with "sub" meaning under and "scapula" meaning wing bone. It is the largest and strongest of the four rotator cuff muscles, which also include the supraspinatus, infraspinatus, and teres minor muscles.
The subscapularis originates at the subscapular fossa, specifically at the medial and lower two-thirds of the groove on the lateral border. The muscle fibres pass laterally from its origin, narrowing towards a tendon that inserts into the lesser tubercle of the humerus and the front of the shoulder joint capsule. The subscapularis is the only rotator cuff muscle that has this function.
The subscapularis muscle plays a crucial role in the stabilisation of the shoulder joint. It contributes to the fixation of the proximal humerus during movements of the elbow, wrist, and hand. The muscle's primary function is internal rotation, but it can also aid in adducting the humerus. The arm's position significantly impacts the actions of this muscle. When the arm is raised, the subscapularis pulls the humerus forward and downward.
The subscapularis nerve innervates the muscle, and the subscapular artery, a branch of the axillary artery, provides its primary blood supply. The subscapularis tendon lies approximately 3 to 5 cm under the surface, which is quite deep for ultrasonography.
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Its primary function is internal rotation
The subscapularis muscle is a large and powerful triangle-shaped muscle that fills the subscapular fossa of the scapula (wing bone). It is the largest and strongest of the four rotator cuff muscles. The other three muscles are the supraspinatus, infraspinatus, and teres minor. The subscapularis muscle's primary function is internal rotation, but it can also aid in adducting the humerus.
The subscapularis muscle is responsible for the internal or medial rotation of the humerus, specifically. This means that it turns the arm inward toward the body at the shoulder joint. This movement is crucial for various activities and sports that require a wide range of arm motions, such as throwing or swimming. The subscapularis is the only muscle of the rotator cuff that has this specific function.
The subscapularis muscle originates at the subscapular fossa, which is located on the anterior surface of the scapula. The muscle fibres then pass laterally, narrowing down to form a tendon that inserts into the lesser tubercle of the humerus. This tendon can be found at the front of the shoulder joint capsule. The subscapularis tendon lies approximately 3 to 5 cm under the surface, which is quite deep for ultrasonography.
The subscapularis muscle is innervated by the subscapular nerve, which provides signals for muscle contraction and relaxation. The primary blood supply to the subscapularis muscle is the subscapular artery, a branch of the axillary artery. This artery ensures that the muscle receives sufficient oxygen and nutrients to function optimally.
In terms of clinical examination, there is no single test that can effectively isolate the action of the subscapularis muscle from other medial rotators of the shoulder joint. However, the Gerber Lift-off test, also known as Gerber's test, is commonly used to examine the subscapularis for potential tears or injuries. This test involves internally rotating the shoulder and placing the dorsum of the hand against the lower back.
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It is covered by a dense fascia
The subscapularis muscle is a large, powerful, triangle-shaped muscle that fills the subscapular fossa. It is the largest and strongest part of the four rotator cuff muscles. The other three muscles are the supraspinatus, infraspinatus, and teres minor. The subscapularis muscle is covered by a dense fascia that attaches to the scapula at the margins of the subscapularis' attachment (origin) on the scapula. The muscle's fibres pass laterally from its origin before coalescing into a tendon of insertion. The tendon intermingles with the glenohumeral (shoulder) joint capsule.
The subscapularis tendon lies approximately 3 to 5 cm under the surface. It is quite deep for ultrasonography, but a highly penetrative 5 MHz linear applicator can be used to examine the muscle. The subscapularis bursa separates the subscapularis from the serratus anterior. The central part of the muscle is crossed by the axillary nerve, axillary artery, and vein. The posterior surface of the muscle's tendon is blended with the fibrous capsule of the glenohumeral joint.
The subscapularis muscle forms the majority of the posterior wall of the axilla. The serratus anterior covers its superolateral part, while the coracobrachialis and biceps brachii muscles lie over its inferomedial part. The subscapularis comprises the anterior border of the upper triangular space, which is completed by the teres major, teres minor, and the long head of the triceps brachii. This space serves as a passageway for the radial nerve and deep brachial artery.
The subscapularis is innervated by the upper and lower subscapular nerves (C5-C6), which stem from the brachial plexus. The subscapular artery, a branch of the axillary artery, provides blood to the subscapularis muscle.
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The subscapularis nerve innervates the muscle
The subscapularis muscle is a large triangular muscle that fills the subscapular fossa and inserts into the lesser tubercle of the humerus. The subscapularis nerve innervates the muscle. The subscapularis nerve is comprised of the upper and lower subscapular nerves (C5-C6), which stem from the brachial plexus. The brachial plexus is a network of nerves that originate in the neck and supply the arm and shoulder. The upper subscapular nerve comes from the superior cord of the brachial plexus, while the lower subscapular nerve comes from the posterior cord.
The subscapularis muscle is one of four muscles that make up the rotator cuff, along with the supraspinatus, infraspinatus, and teres minor. The rotator cuff muscles work together to stabilize and steer the humeral head within the glenoid cavity during movement of the upper limb. Each muscle also has its own specific role, and the subscapularis muscle's primary function is internal rotation of the humerus, although it can also aid in adduction.
The subscapularis muscle is located at the anterior surface of the scapula and originates at the subscapular fossa, specifically the medial and lower two-thirds of the groove on the lateral border. The muscle fibres transition into a tendon, which inserts onto the lesser tubercle of the humerus in front of the joint capsule. The subscapular artery, a branch of the axillary artery, provides the primary blood supply to the subscapularis muscle.
The subscapularis muscle is subject to various injuries and conditions, such as tendonitis, which can cause pain when moving the shoulder, especially when the arm is raised above the shoulders. There are several clinical tests available to examine the subscapularis muscle, including the Gerber Lift-off test and the bear hug test. These tests can help diagnose tears or other issues with the muscle.
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Frequently asked questions
The subscapularis is a large, powerful, triangle-shaped muscle that fills the subscapular fossa and inserts into the lesser tubercle of the humerus. It is one of the four muscles that compose the rotator cuff apparatus.
The primary function of the subscapularis muscle is internal rotation, but it can also aid in adducting the humerus. It helps in shoulder adduction and extension in certain positions.
The subscapularis muscle gets its name from its orientation under the scapula ("sub" meaning under, and "scapula" meaning wing bone).
