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The subscapularis muscle is a large, powerful, triangle-shaped muscle that originates at the subscapular fossa and inserts at the lesser tubercle of the humerus. It is one of the four muscles that compose the rotator cuff apparatus, along with the supraspinatus, infraspinatus, and teres minor muscles. The subscapularis muscle's primary function is internal rotation, and it also aids in adducting the humerus. This muscle is part of the rotator cuff and helps to stabilise the shoulder joint. Given this information, is the subscapularis a SITS muscle?
| Characteristics | Values |
|---|---|
| Muscle name | Subscapularis |
| Muscle shape | Triangle |
| Muscle size | Large |
| Muscle power | Powerful |
| Muscle origin | Subscapular fossa |
| Muscle insertion | Lesser tubercle of the humerus |
| Muscle nerve | Subscapular nerve |
| Muscle artery | Subscapular artery |
| Muscle function | Internal rotation |
| Muscle stabilisation | Shoulder joint |
| Muscle action | Adducting the humerus |
| Muscle location | Under the scapula |
| Muscle composition | Four rotator cuff muscles |
| Muscle treatment | Non-operative |
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What You'll Learn
The subscapularis is a large triangular muscle
The subscapularis muscle's primary function is internal rotation, but it also assists in adducting the humerus and plays a significant role in shoulder joint stability. The muscle's 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. This tendon intermingles with the glenohumeral (shoulder) joint capsule, contributing to the fixation of the proximal humerus during movements of the elbow, wrist, and hand.
The subscapularis muscle is susceptible to injuries such as tendonitis and tendinopathy, which can cause pain and tenderness in the shoulder, especially when the arm is raised above the shoulders. The muscle and tendon are also vulnerable to trauma and wear and tear from overuse or misuse. The subscapularis tendon lies approximately 3 to 5 cm under the surface, making it challenging to examine using standard ultrasonography techniques. However, specialised procedures, such as the one developed by Mack et al., can provide a detailed examination of the muscle and tendon.
The subscapularis muscle is innervated by the subscapular nerve, with blood supplied by the subscapular artery, a branch of the axillary artery. Lymph drainage from the muscle flows into the axillary nodes. The subscapularis muscle is an essential component of the human body's movement and stability, particularly in the shoulder region, and its unique structure and functions make it a fascinating subject in anatomy and physiology.
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It is one of the four rotator cuff (SITS) muscles
The subscapularis muscle is indeed one of the four muscles that compose the rotator cuff apparatus, or rotator cuff interval. The other three muscles are the supraspinatus, infraspinatus, and teres minor muscles.
The subscapularis is a large, powerful, and strong triangle-shaped muscle that fills the subscapular fossa of the scapula. The muscle gets its name from its position under the scapula, or wing bone. The subscapularis is the largest and strongest of the four rotator cuff muscles. It is also the only rotator cuff muscle that has an internal or medial rotation function.
The subscapularis muscle's primary function is the internal rotation of the humerus, or arm. It also aids in shoulder adduction and extension in certain positions. When the arm is raised, the subscapularis pulls the humerus forward and downward. The subscapularis stabilises the shoulder joint by contributing to the fixation of the proximal humerus during movements of the elbow, wrist, and hand. The subscapularis nerve innervates the muscle, and the subscapular artery provides its blood supply.
The subscapularis tendon lies approximately 3 to 5 cm under the surface. The tendon intermingles with the glenohumeral (shoulder) joint capsule. The subscapularis bursa separates the subscapularis tendon from the neck of the scapula.
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Its primary function is internal rotation
The subscapularis muscle is a large, powerful, triangle-shaped muscle that fills the subscapular fossa of the scapula. Its name is derived from its orientation under the scapula: sub (under) and scapula (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 muscle's primary function is internal rotation, but it can also aid in adducting the humerus. This internal rotation function is unique to the subscapularis among the rotator cuff muscles. When the subscapularis muscle contracts, it internally or medially rotates the humerus. The arm position significantly affects 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 is an important stabiliser of the shoulder joint. It helps to hold the head of the humerus in the glenoid fossa of the scapula during movements of the upper limb. This function prevents the upward migration of the humeral head and prevents anterior displacement of the humerus. The subscapularis also plays a role in shoulder adduction and extension in certain positions.
The subscapularis muscle is susceptible to injury, with tendinitis and tendinopathy being common conditions associated with this muscle. Symptoms of subscapularis tendinitis include pain when moving the shoulder, especially when the arm is raised above the shoulders. A positive bear-hug test, belly press test, or lift-off test indicates significant tearing of the subscapularis muscle. Treatment for partial tears and tendinopathies typically involves non-operative management, including rest, activity modification, analgesics, ice, and physical therapy. However, surgical intervention may be required in cases of full-thickness tears or for athletes who require full function of the muscle.
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It is susceptible to trauma and overuse
The subscapularis muscle is the largest and strongest of the four rotator cuff muscles. It is a powerful, triangular-shaped muscle that fills the subscapular fossa and inserts into the lesser tubercle of the humerus. Its primary function is internal rotation, and it also aids in adducting the humerus. The subscapularis is susceptible to trauma and overuse, which can result in tears and tendon injuries.
Tears in the subscapularis muscle can occur due to several factors, including overuse, trauma, or age-related conditions. In younger individuals, tears typically arise from injuries or traumatic events, such as falls, sports injuries, or car accidents. Sporting events are a common cause of subscapularis tears, along with other muscles in the rotator cuff. Work-related injuries are also a factor, particularly in active males in their third to fifth decades of life.
Overuse of the subscapularis muscle can lead to tendonitis symptoms, including pain when moving the shoulder, especially when the arm is raised above the shoulders. An overworked subscapularis muscle can cause a feeling of inability to lift the arm and may even result in a frozen shoulder. Tendonitis and tendinopathy are typically managed through conservative treatments such as rest, activity modification, analgesics, ice, and physical therapy.
Trauma to the subscapularis muscle can cause tears or tendon injuries. Tendon tears may occur as a result of specific traumatic events or shoulder surgery. When the subscapularis tendon is repaired during surgery, it can become susceptible to tears if not appropriately addressed. Tears can vary in size, and treatment options depend on the severity and impact on the patient's life. Conservative treatments, such as rest, physical therapy, and anti-inflammatory medications, are often recommended for mild to moderate tears. However, in cases of full-thickness tears or significant disability, surgery may be necessary to repair the tear and reattach the tendon to its normal position.
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The subscapularis nerve innervates the muscle
The subscapularis muscle is a large, powerful, and triangle-shaped muscle that fills the subscapular fossa and inserts into the lesser tubercle of the humerus. It is the largest and most powerful muscle in the rotator cuff. The subscapularis nerve innervates the muscle. The subscapular nerve is made up of two branches, the upper subscapular nerve (USN) and the lower subscapular nerve (LSN). The USN is the most consistent, with a limited amount of anatomic variation. The LSN has a much larger variance.
The subscapularis nerve is responsible for the internal rotation of the humerus and plays a role in shoulder adduction and extension. The arm's position affects 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 nerve is a branch of the brachial plexus, which is formed by the ventral rami of the lower four cervical and upper thoracic nerve roots. These ventral rami fuse to form an upper, middle, and lower trunk, which then split into anterior and posterior divisions. The posterior divisions further split into three cords: medial, lateral, and posterior. The subscapularis nerve arises from the posterior cord of the brachial plexus.
The subscapularis muscle is involved in the formation of three intermuscular axillary spaces: the quadrangular space, the upper triangular space, and the lower triangular space. The subscapularis forms the anterior boundary of the quadrangular space, while the shoulder joint capsule and teres minor form the superior boundary. The subscapularis makes up the anterior border of the upper triangular space, with the teres major, long head of the triceps brachii, and the humerus forming the posterior, medial, and lateral borders, respectively. In the lower triangular space, the subscapularis again acts as the anterior border, with the teres major, long head of the triceps brachii, and the humerus forming the posterior, medial, and lateral borders.
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Frequently asked questions
The subscapularis muscle is a large, powerful, triangle-shaped muscle that fills the subscapular fossa of the scapula. It is one of the four muscles that compose the rotator cuff apparatus.
The subscapularis muscle's primary function is internal rotation, but it can also aid in adducting the humerus. It helps in shoulder adduction and extension in certain positions.
Yes, the subscapularis is one of the four SITS muscles, along with the supraspinatus, infraspinatus, and teres minor muscles. These muscles work together to stabilize the glenohumeral joint.
