Logan Steele
The scapula, commonly referred to as the shoulder blade, is a flat, triangular bone that sits above the rib cage in the upper back. It is surrounded and supported by a complex system of muscles that work together to help move the arm. These muscles can be categorised into three groups: intrinsic, extrinsic, and stabilising and rotating muscles. The intrinsic muscles of the scapula include the rotator cuff muscles, which are the supraspinatus, infraspinatus, subscapularis, and teres minor. These muscles attach to the surface of the scapula and are responsible for the internal and external rotation of the shoulder joint. The extrinsic muscles include the biceps, triceps, and deltoid muscles, which attach to the coracoid process and spine of the scapula. The third group, which is mainly responsible for stabilisation and rotation of the scapula, consists of the trapezius, serratus anterior, levator scapulae, and rhomboid muscles.
| Characteristics | Values |
|---|---|
| Description | Thick, flat, triangular bone lying on the thoracic wall |
| Location | Upper back, above the rib cage |
| Function | Provides attachment for muscles and three groups of muscles: intrinsic, extrinsic, and stabilizing and rotating muscles |
| Intrinsic Muscles | Rotator cuff (subscapularis), supraspinatus, infraspinatus, teres minor, teres major |
| Extrinsic Muscles | Biceps, triceps, deltoid |
| Stabilizing and Rotating Muscles | Trapezius, serratus anterior, levator scapulae, rhomboids |
| Synergists for Upward Rotation | Upper and lower trapezius, serratus anterior |
| Protraction | Serratus anterior, pectoralis major and minor |
| Retraction | Trapezius, rhomboids, latissimus dorsi |
| Elevation | Trapezius, levator scapulae, rhomboids |
| Depression | Latissimus dorsi, serratus anterior, pectoralis major and minor, trapezius |
| Upward Rotation | Trapezius, serratus anterior |
| Downward Rotation | Latissimus dorsi, levator scapulae, rhomboids, pectoralis major and minor |
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What You'll Learn
- The supraspinatus, infraspinatus, subscapularis, and teres minor/major are the four rotator cuff muscles
- The serratus anterior, pectoralis major, and pectoralis minor muscles are responsible for protraction
- Retraction is accomplished by the trapezius, rhomboids, and latissimus dorsi muscles
- The trapezius, levator scapulae, and rhomboid muscles are responsible for elevation
- Depression is accomplished by the latissimus dorsi, serratus anterior, pectoralis major and minor, and trapezius muscles
The supraspinatus, infraspinatus, subscapularis, and teres minor/major are the four rotator cuff muscles
The supraspinatus, infraspinatus, subscapularis, and teres minor are the four muscles that make up the rotator cuff. They are often referred to as the "SITS" muscles, a helpful mnemonic to remember their names. These muscles play important roles in the health and function of the shoulder. They start on the shoulder blade (scapula) and join as tendons to form a thick covering at the top of the humerus (the bone in the upper arm).
The supraspinatus muscle originates above the spine of the shoulder blade and inserts on the greater tuberosity of the humerus. It is responsible for abducting (elevating) the shoulder joint out to the side. The infraspinatus muscle originates below the spine of the scapula in the infraspinatus fossa and inserts on the posterior aspect of the greater tuberosity of the humerus. It is a powerful lateral rotator of the humerus. The subscapularis muscle originates on the anterior, or front surface, of the scapula, sitting directly over the ribs, and inserts on the lesser tuberosity of the humerus. It is the largest component of the posterior wall of the axilla and prevents the anterior dislocation of the humerus during abduction while medially rotating the humerus. The teres minor muscle originates on the lateral scapula border and inserts on the inferior aspect of the greater tuberosity of the humerus. It works with the infraspinatus to externally rotate the shoulder.
The rotator cuff has several important functions, including stabilizing the shoulder, elevating and rotating the arm, and ensuring the head of the humerus stays securely placed in the shoulder socket. When the rotator cuff muscles are strong, they prevent the humerus bone from overly depressing or elevating, maintaining smooth motion in the shoulder joint. Conversely, when these muscles are weak or injured, it can cause pain and trouble using the shoulder.
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The serratus anterior, pectoralis major, and pectoralis minor muscles are responsible for protraction
The scapula, or shoulder blade, is a flat, triangular bone that connects the clavicle to the humerus. It forms the posterior of the shoulder girdle and provides attachment to several groups of muscles, including the serratus anterior, pectoralis major, and pectoralis minor. These muscles are responsible for protraction, the movement of the scapula towards the midline of the body.
The serratus anterior is a fan-shaped muscle that originates on the superolateral surfaces of the first to eighth or ninth ribs at the lateral wall of the thorax. It inserts along the superior angle, medial border, and inferior angle of the scapula and is a key scapular stabiliser, keeping the shoulder blades against the ribcage at rest and during movement. The serratus anterior also contributes to upward rotation and external rotation of the scapula during arm elevation. Weakness or inhibition of the serratus anterior can impair protraction and upward rotation of the scapula, limiting the overhead range of motion and reducing overall scapular/shoulder stability.
The pectoralis major and pectoralis minor muscles are also involved in protraction. The pectoralis minor functions as a synergist of the serratus anterior, although the extent of its activation during exercises targeting the serratus anterior is unclear. The pectoralis minor is inserted into the medial border and superior surface of the coracoid process.
Protraction, retraction, elevation, depression, upward rotation, and downward rotation are the six motions that allow for the full function of the shoulder joint, one of the most mobile and versatile joints in the human body. The scapula must be able to rotate upwardly, posteriorly tilt, and externally rotate to achieve the full 180 degrees of elevation of the arm. Any disturbance in this rhythm can lead to decreased scapulothoracic movement and issues such as fatigue, impingement, instability, and limits in elevation.
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Retraction is accomplished by the trapezius, rhomboids, and latissimus dorsi muscles
The scapula, or shoulder blade, is a sturdy, flat, triangular bone that connects the clavicle to the humerus. It forms the posterior of the shoulder girdle. The scapula provides attachment to several groups of muscles, including the levator scapulae, trapezius, rhomboids, and serratus anterior. These muscles are responsible for the rotational movements and stabilization of the scapula.
The scapula engages in six types of motion, allowing for full-functional upper extremity movement: protraction, retraction, elevation, depression, upward rotation, and downward rotation. Retraction is accomplished by the trapezius, rhomboids, and latissimus dorsi muscles. The trapezius muscle is a large muscle that spreads across the entire back and is crucial for proper scapula positioning. The rhomboids are responsible for scapular retraction and are important for the movement of the upper extremity and overall stabilization of the shoulder. The latissimus dorsi is a climbing muscle that assists in holding the scapula against the thorax during upper limb movements.
Weakness in these three muscles can lead to poor scapular retraction. Exercises such as rows and "I-Y-T" movements can help strengthen the rhomboids, trapezius, and latissimus dorsi, improving scapular retraction.
Scapular retraction is a simple yet important movement that enhances upper back muscles and exercises. It aids in improving posture, which can help alleviate back and shoulder pain.
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The trapezius, levator scapulae, and rhomboid muscles are responsible for elevation
The scapula, or shoulder blade, is a flat, triangular bone that connects the clavicle to the humerus. It forms the posterior of the shoulder girdle. The scapula provides attachment points for three groups of muscles: intrinsic, extrinsic, and stabilising and rotating muscles.
The intrinsic muscles of the scapula include the muscles of the rotator cuff: the subscapularis, supraspinatus, infraspinatus, and teres minor. These muscles attach to the surface of the scapula and are responsible for the internal and external rotation of the shoulder joint, along with humeral abduction.
The extrinsic muscles include the biceps, triceps, and deltoid muscles. They attach to the coracoid process and supraglenoid tubercle of the scapula, the infraglenoid tubercle of the scapula, and the spine of the scapula. These muscles are responsible for several actions of the glenohumeral joint.
The third group of muscles, which is mainly responsible for stabilisation and rotation of the scapula, consists of the trapezius, levator scapulae, and rhomboid muscles. These muscles are also responsible for elevation of the scapula.
The trapezius is a large, triangular muscle that covers the upper back, shoulders, and neck. It has several origin points along the midline of the posterior neck and back, including the spinous process of C7-T12 of the spine, ligamentum nuchae, scapulae, clavicles, and ribs. The superior fibres attach to the skull and neck. The trapezius muscle is involved in movements of the shoulder girdle and is therefore considered a muscle of the upper limb rather than the back. It stabilises and moves the scapula, with the upper fibres elevating and upwardly rotating the scapula and extending the neck. The middle fibres adduct the scapula, and the lower fibres depress and aid the upper fibres in upwardly rotating the scapula.
The levator scapulae attaches at the superior angle of the scapula. Along with the descending fibres of the trapezius, it produces an elevation of the scapula at the scapulothoracic joint. It also helps to maintain the level of the shoulders against gravity, such as when carrying a weight in the hand.
The rhomboids are two bilateral, superficial muscles located in the upper back: the rhomboid minor and rhomboid major. They extend between the nuchal ligament, spinous processes of thoracic vertebrae, and scapula. The rhomboids primarily retract the scapula superomedially and rotate the glenoid cavity. They are important for stabilising the scapula and reinforcing the shoulder.
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Depression is accomplished by the latissimus dorsi, serratus anterior, pectoralis major and minor, and trapezius muscles
The scapula, or shoulder blade, is a flat, triangular bone that connects the clavicle to the humerus. It is a critical component of the shoulder joint, enabling a full range of motion in the upper extremity. The scapula engages in six types of motion: protraction, retraction, elevation, depression, upward rotation, and downward rotation.
Depression is one of the six motions of the scapula and is accomplished by the latissimus dorsi, serratus anterior, pectoralis major and minor, and trapezius muscles. These muscles work together to depress the scapula, allowing for a full range of motion in the shoulder joint.
The latissimus dorsi is a large, flat muscle that originates from the inferior angle of the scapula. It is an extrinsic muscle of the scapula and is also involved in retraction and downward rotation of the scapula. Injury to the thoracodorsal nerve can result in paralysis of the latissimus dorsi, leading to an inability to actively depress the shoulder.
The serratus anterior is an intrinsic muscle of the scapula that originates on the upper ribs and inserts along the medial border of the scapula. It plays a crucial role in scapular protraction, upward rotation, and depression. The serratus anterior also works with the trapezius muscle to optimize scapula position and scapulohumeral rhythm.
The pectoralis major and minor muscles are also involved in scapular protraction and depression. They are extrinsic muscles of the scapula and are located in the anterior area of the shoulder joint.
The trapezius muscle is a large, flat muscle that inserts into the upper border of the scapula. It is an intrinsic muscle of the scapula and is responsible for scapular retraction, elevation, and depression. The trapezius muscle also assists in active movements such as side bending and turning the head, as well as internally rotating the arm.
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Frequently asked questions
The pectoralis minor, coracobrachialis, and the short head of the biceps brachii.
The rhomboids major and minor.
The serratus anterior.
The subscapularis.
The infraspinatus.
