Logan Steele
The subscapularis is a large, triangular-shaped muscle located in the subscapular fossa of the scapula (wingbone). It is the largest and most powerful of the four rotator cuff muscles, which also include the supraspinatus, infraspinatus, and teres minor muscles. The subscapularis plays a crucial role in shoulder motion and stabilization, with its primary function being the internal rotation of the humerus. Its tendon lies approximately 3 to 5 cm under the surface, and it is supplied by the upper and lower subscapular nerves.
| Characteristics | Values |
|---|---|
| Shape | Triangular |
| Location | Subscapular fossa of scapula |
| Function | Internal rotation of the humerus, shoulder adduction and extension |
| Blood Supply | Subscapular artery |
| Nerve Supply | Upper and lower subscapular nerves (C5-C6) |
| Tendons | Inserts into the lesser tubercle of the humerus and the front of the shoulder joint capsule |
| Muscle Unit | Teres major muscle |
| Actions | Abduction, adduction, and stabilization of the shoulder joint |
| Test for Examination | Gerber Lift-off test, Bear hug test |
| Tendon Tear | Uncommon, part of a large rupture of the rotator cuff |
| Imaging Techniques | MRI, US, Ultrasonography |
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What You'll Learn
The subscapularis is a large triangular muscle
The subscapularis muscle is located in the subscapular fossa at the anterior aspect of the scapula. It contains multiple tendinous and muscular bundles that merge laterally into a flattened tendon in the upper two-thirds of the muscle. This tendon has a variable insertion, mostly on the lesser tuberosity of the humerus, but also on the greater tuberosity and the bicipital groove. The subscapularis tendon lies approximately 3 to 5 cm under the surface.
The subscapularis is covered by a dense fascia that attaches to the scapula at the margins of the muscle's attachment. 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. A bursa intervenes between the tendon and a bare area at the lateral angle of the scapula/the neck of the scapula. The subscapularis (supraserratus) bursa separates the subscapularis from the serratus anterior.
The primary function of the subscapularis is the internal rotation of the humerus. It helps in shoulder adduction and extension in certain positions. Arm position has a marked effect on the actions caused by this muscle: when the arm is raised, the subscapularis pulls the humerus forward and downward. When the humerus is in a fixed position, the insertion of the subscapularis can act as an origin, producing abduction of the inferior border of the scapula.
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It fills the subscapular fossa and inserts into the humerus
The subscapularis muscle is a large, powerful, and triangular shoulder muscle. It is the largest and strongest muscle of the rotator cuff, a group of four muscles that also includes the supraspinatus, infraspinatus, and teres minor. The rotator cuff muscles work together to stabilize and steer the humeral head within the glenoid cavity during various movements of the upper limb.
The subscapularis muscle is located in the subscapular fossa of the scapula, which is the wing bone. It fills the subscapular fossa and extends to the lesser tubercle of the humerus and the front of the capsule of the shoulder joint. The muscle fibres pass laterally from its origin in the scapula before coalescing into a tendon of insertion.
The subscapularis muscle is covered by a dense fascia that attaches to the scapula at the margins of the muscle's attachment. The subscapular bursa, which 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 plays a crucial role in the internal rotation and adduction of the humerus. When the arm is raised, the subscapularis muscle draws the humerus forward and downward. Additionally, it helps stabilize the shoulder joint by contributing to the fixation of the proximal humerus during movements of the elbow, wrist, and hand.
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The muscle's fibres pass laterally
The subscapularis muscle is a large, triangular-shaped muscle that fills the subscapular fossa of the scapula. It is the largest and strongest of the four rotator cuff muscles. The muscle fibres pass laterally from their origin, with the medial two-thirds of the fibres originating from the subscapular fossa of the scapula. The subscapularis muscle is covered by a dense fascia, which attaches to the scapula at the margins of the muscle's attachment.
The lateral passage of the muscle fibres is an important anatomical feature of the subscapularis muscle. The fibres coalesce into a tendon of insertion, which intermingles with the glenohumeral (shoulder) joint capsule. This tendon passes through the subscapular bursa, a cavity that separates the subscapularis tendon from the neck of the scapula.
The lateral passage of the muscle fibres is also significant in the function of the subscapularis muscle. The muscle's primary function is the internal rotation of the humerus, and it assists in shoulder adduction and extension. The lateral coalescence of the fibres into a tendon allows for a smooth and efficient transmission of force during these movements.
Additionally, the lateral aspect of the subscapularis muscle is relevant in the clinical evaluation of the muscle. The Gerber Lift-off test and the bear hug test are used to examine the subscapularis muscle for potential tears. Imaging techniques such as ultrasonography and MRI can also be utilised to visualise the muscle and its tendon, particularly through external rotation and medial approaches.
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It is covered by a dense fascia
The subscapularis muscle is a large, triangular shoulder muscle located in the subscapular fossa of the scapula. It attaches between the scapula and the proximal humerus. The subscapularis is covered by a dense fascia, which is a sheath of stringy connective tissue that surrounds and supports every structure in the body. Fascia is present throughout the inside of the body, attaching to and stabilising every muscle, tendon, ligament, bone, organ and tissue. It is similar to tendons and ligaments in that it is mostly made of collagen, but its location and function differ.
Deep fascia surrounds the musculoskeletal system, covering muscles, bones, tendons, cartilage, nerves and blood vessels. It is thicker than superficial fascia, which is located directly under the skin. Deep fascia is commonly more fibrous and has a higher concentration of hyaluronan compared to other subtypes. It forms into sheets of pearly-white fibrous tissue to attach muscles needing a wide area of attachment. Aponeurotic fascia is thick, pearly-white tissue that separates more easily from muscles. Epimysial fascia is thinner and more tightly connected to muscles.
The subscapularis muscle is innervated by the upper and lower subscapular nerves (C5-C6), which are branches of the posterior cord of the brachial plexus. The muscle's medial two-thirds originate from the subscapular fossa of the scapula and several tendinous intramuscular septa. The subscapularis tendon lies approximately 3 to 5 cm under the surface. The subscapularis is supplied by the upper and lower subscapular nerves (C5-C6), branches of the posterior cord of the brachial plexus.
The subscapularis medially (internally) rotates the humerus and adducts it. When the arm is raised, the subscapularis draws the humerus forward and downward. It stabilises the shoulder joint by contributing to the fixation of the proximal humerus during movements of the elbow, wrist and hand. The subscapularis is one of four muscles that make up the rotator cuff, along with the supraspinatus, infraspinatus and teres minor.
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The subscapularis is the largest, strongest muscle of the rotator cuff
The subscapularis muscle is a large triangular-shaped muscle that sits at the anterior surface of the scapula. The subscapularis is the largest and strongest muscle of the four rotator cuff muscles. The other three are the supraspinatus, infraspinatus, and teres minor muscles. The subscapularis muscle's primary function is internal rotation, but it can also aid in adducting the humerus.
The subscapularis muscle is a powerful lateral rotator of the humerus. It originates at the subscapular fossa, specifically the medial and lower two-thirds of the groove on the lateral border. The muscles transition to a tendon, which inserts on the lesser tubercle of the humerus in front of the joint capsule. The subscapularis is the only rotator cuff muscle with this function.
The subscapularis muscle plays an important role in shoulder movement and stability. Arm position has a marked effect on the actions caused by this muscle. When the arm is raised, the subscapularis pulls the humerus forward and downward. When the humerus is in a fixed position, the insertion of the subscapularis can act as an origin, producing abduction of the inferior border of the scapula.
The subscapularis muscle can be injured by throwing or overhead athletes. Tendonitis, tendinopathy, and tears are common causes of shoulder pain due to subscapularis issues. An overworked subscapularis muscle may make you feel like you are unable to lift your arm. This is sometimes referred to as a "frozen shoulder".
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Frequently asked questions
The subscapularis is a large, triangular-shaped muscle that fills the subscapular fossa and is located in the shoulder.
The subscapularis muscle's primary function is the internal rotation of the humerus. It helps with shoulder adduction and extension.
The subscapularis is the largest and strongest of the four rotator cuff muscles. It plays a crucial role in shoulder motion and stabilization.
The established clinical test for examining the subscapularis muscle is the Gerber Lift-off test. The bear hug test is also used to check for subscapularis muscle tears.
The subscapularis muscle may be injured by throwing actions. Tendon tears and tendonitis are also associated with this muscle.
