The musculocutaneous nerve is relatively protected in the axilla, hence injury to it is uncommon. A stab wound in the axilla is the most prevalent source of damage. Because of the activities of the pectoralis major and deltoid, the brachioradialis, and the supinator muscles, arm flexion and forearm flexion and supination are diminished but not completely lost. Over the lateral part of the forearm, there is a lack of sensation.

A suprascapular nerve injury causes numbness in the shoulder, as well as weakness in abduction and external rotation. Damage to the axillary nerve can result in shoulder or arm muscle weakness, as well as difficulty lifting the arm. This is because the deltoid and supraspinatus muscles, which are innervated by the axillary and suprascapular nerves, are responsible for abduction of the arm at the shoulder joint.

Fracture dislocations of the elbow appear extremely complex, and identification of the basic injury patterns can facilitate management. The simplest pattern of elbow fracture dislocation is posterior dislocation of the elbow with fracture of the radial head. Addition of a coronoid fracture, no matter how small, to elbow dislocation and radial head fracture is called the terrible triad of the elbow.

Damage to the long thoracic nerve results in weakness/paralysis of the serratus anterior muscle causing difficulty abducting the upper limb above 90 degrees and giving a ‘winged ‘ scapula appearance where the medial border, particularly the inferior angle, of the scapula moves laterally and posteriorly away from the thoracic wall (this becomes more pronounced if the patient presses the upper limb against a wall).

Extensor carpi radialis brevis is a fusiform muscle found in the lateral part of the posterior forearm. Together with anconaeus, brachioradialis, extensor carpi radialis longus, extensor digitorum, extensor digiti minimi and extensor carpi ulnaris, it belongs to the superficial forearm extensor group. Extensor carpi radialis brevis originates from the lateral epicondyle of humerus via the common extensor tendon. This is a common origin that it shares with the extensor digitorum, extensor digiti minimi and extensor carpi ulnaris muscles. Some fibres also originate from the lateral intermuscular septum, a thick aponeurosis that covers the muscle itself, and from the radial collateral ligament.The muscle courses inferiorly, giving off a long tendon in the middle of the forearm which descends towards the dorsal hand. The tendon passes through a groove on the posterior surface of radius, deep to the extensor retinaculum. After traversing the extensor retinaculum space, the tendon inserts into the posterior aspect of the base of the third metacarpal bone.Extensor carpi radialis brevis is innervated directly by the radial nerve (C5- C8), or sometimes from its deep branch/posterior interosseous nerve. The radial nerve stems from the posterior cord of the brachial plexus.The muscle is vascularized by the radial recurrent artery, radial artery and deep brachial artery (via its radial collateral branch).Extensor carpi radialis brevis works together with extensor carpi ulnaris and extensor carpi radialis longus to extend the hand at the wrist joint. This action is vital in a sequence of muscle contractions needed for clenching a fist or making a grip. When performing these functions, wrist extension blocks the flexor muscles from on acting upon the hand. Instead, flexors act only on the digits, thereby flexing them and producing an effective hand grip, such as that seen in a tennis backhand. When the extensor carpi radialis brevis muscle contracts together with extensor carpi radialis longus and flexor carpi radialis, it contributes to producing hand abduction (radial deviation).

Fracture of the medial epicondyle is most likely to result in damage to the ulnar nerve. The three hypothenar muscles, two medial lumbricals, seven interossei, the adductor pollicis, and the deep head of the flexor pollicis brevis are all innervated by the deep branch of the ulnar nerve.

Abductor pollicis longus is a muscle found in the posterior compartment of the forearm. It is one of the five deep extensors in the forearm, along with the supinator, extensor pollicis brevis, extensor pollicis longus and extensor indicis.Abductor pollicis longus is innervated by the posterior interosseous nerve (C7, C8), which is a continuation of the deep branch of the radial nerve. The radial nerve is a branch of the posterior cord of the brachial plexus.Blood supply to the abductor pollicis longus muscle comes from the interosseous branches of the ulnar artery.Acting alone or with abductor pollicis brevis, abductor pollicis longus pulls the thumb away from the palm. More specifically, it produces (mid-) extension and abduction of the thumb at the first metacarpophalangeal joint. This action is seen in activities such as bowling and shovelling.Working together with the long and short extensors of the thumb, the muscle also helps to fully extend the thumb at the metacarpophalangeal joint. This action is important for loosening the hand grip, for example, when letting go of objects previously being held. Abductor pollicis longus also helps to abduct the hand (radial deviation) at the radiocarpal joint.

Pronator quadratus is a deep-seated, short, flat, and quadrilateral muscle with fibres running in a parallel direction. It arises from the oblique ridge on the anterior surface of the distal fourth of the Ulna. It is inserted in lateral border and anterior surface of the distal fourth of the radius. It is innervated by the anterior interosseous nerve, a branch of the median nerve (C8-T1). It is vascularized by the anterior interosseous artery.The action of the pronator quadratus muscle along with the pronator teres result in the pronation of the radioulnar joint. Contraction of this muscle pulls the distal end of the radius over the ulna, resulting in the pronation of the radioulnar joint

Damage to the central slip of the extensor digitorum tendon would result in loss of extension at the proximal interphalangeal joint resulting in a fixed flexion deformity of this joint, and hyperextension of the distal interphalangeal joint due to a loss of balancing forces. This is called the Boutonniere deformity.

Damage to the insertion of the terminal extensor digitorum tendon would result in loss of extension at the distal interphalangeal joint causing a fixed flexion deformity, called the Mallet deformity.

The pectoralis major is a muscle that runs across the top of the chest and connects to a ridge on the back of the humerus (the bone of the upper arm). Adduction, or lowering, of the arm (opposed to the deltoideus muscle) and rotation of the arm forward around the axis of the body are two of its main functions.

The pectoralis major is the superior most and largest muscle of the anterior chest wall. It is a thick, fan-shaped muscle that lies underneath the breast tissue and forms the anterior wall of the axilla.Its origin lies anterior surface of the medial half of the clavicle, the anterior surface of the sternum, the first 7 costal cartilages, the sternal end of the sixth rib, and the aponeurosis of the external oblique of the anterior abdominal wall.The insertion of the pectoralis major is at the lateral lip of the intertubercular sulcus of the humerus. There are 2 heads of the pectoralis major, the clavicular and the sternocostal, which reference their area of origin. The function of the pectoralis major is 3-fold and dependent on which heads of muscles are involved:- Flexion, adduction and medial rotation of the arm at the glenohumeral joint- Clavicular head causes flexion of the extended arm- Sternoclavicular head causes extension of the flexed armArterial supply of the pectoralis major, the pectoral artery, arises from the second branch of the axillary artery, the thoracoacromial trunk.The 2 heads of the pectoralis major have different nervous supplies. The clavicular head derives its nerve supply from the lateral pectoral nerve. The medial pectoral nerve innervates the sternocostal head. The lateral pectoral nerve arises directly from the lateral cord of the brachial plexus, and the medial pectoral nerve arises from the medial cord.

Free movement of the tendons in the carpal tunnel is facilitated by synovial sheaths, which surround the tendons. All of the tendons of the FDP and FDS are contained within a single synovial sheath with a separate sheath enclosing the tendon of the FPL.

Flexor carpi radialis is innervated by the median nerve.

The palmaris longus is a small, fusiform-shaped muscle located on the anterior forearm of the human upper extremity. The palmaris longus muscle is commonly present but may be absent in a small percentage of the population, ranging from 2.5% to 26% of individuals, depending on the studied population.The palmaris longus belongs to the anterior forearm flexor group in the human upper extremity. The muscle attaches proximally to the medial humeral epicondyle and distally to the palmar aponeurosis and flexor retinaculum. The blood supply to the palmaris longus muscle is via the ulnar artery, a branch of the brachial artery in the human upper extremity.The palmaris longus muscle receives its innervation via branches of the median nerve containing nerve roots C5-T1. Median nerve injury at or above the elbow joint (including brachial plexus and nerve root injury) can lead to deficits in the palmaris longus and other forearm flexor muscles, leading to weakened elbow flexion, wrist flexion, radial deviation, finger flexion, thumb opposition, flexion, and abduction, in addition to the loss of sensory function in the distribution of the median nerve.

Brachioradialis is a fusiform muscle located in the lateral part of the posterior forearm. Along with extensor carpi radialis brevis and extensor carpi radialis longus, it comprises the radial group of forearm muscles, which belong to the superficial layer of posterior forearm muscles. Although anatomically part of the posterior forearm muscles, which are known to be forearm extensors, brachioradialis’ fibre orientation enables it to rather flex the forearm, and aids in supination of the forearm at the radioulnar joint.The brachioradialis muscle originates from the upper two-thirds of the lateral supracondylar ridge of humerus and the anterior surface of the lateral intermuscular septum of the arm. It slides over the lateral surface of the elbow joint, entering the anterolateral cubital area. The muscle fibres course inferiorly down the radial part of the anterior forearm, forming a thick tendon in approximately the middle of the forearm. This tendon then traverses the remainder of the forearm, inserting near the wrist, just proximal to the styloid process of radius.Brachioradialis is innervated by the radial nerve (from the root values C5-C6) that stems from the posterior cord of the brachial plexus. Blood supply to the brachioradialis muscle comes from branches of the radial artery, radial recurrent artery and the radial collateral branch of the deep brachial artery.

The arm should be placed in a poly-sling that should be worn for about two weeks. A physiotherapist may give gentle movements for the arm to help in reducing stiffness and in relieving the pain. It is important that the patient must avoid positions that could cause re-dislocation.The most important position to avoid is the arm being held out at 90 degrees to the side with the palm facing upwards, especially if a force is being applied.

In an anterior dislocation, the arm is an abducted and externally rotated position. In the externally rotated position, the posterosuperior aspect of the humeral head abuts and drives through the anteroinferior aspect of the glenoid rim. This can damage the humeral head, glenoid labrum, or both. An associated humeral head compression fracture is described as a Hill Sach’s lesion. If large enough, it can lead to locked dislocations that may require open reduction. The glenoid labrum is a fibrocartilaginous structure that rings the circumference of the glenoid fossa. Bankart lesions are injuries to the anteroinferior glenoid labrum complex and the most common capsulolabral injury. A bony Bankart lesion refers to an associated fracture of the glenoid rim. These capsulolabral lesions are risk factors for recurrent dislocation.Axillary nerve injury is identified in about 42% of acute anterior shoulder dislocations. Nerve transection is rare, and traction injuries are more common. Arterial injury has also been described. The subclavian artery becomes the axillary artery after passing the first rib. The distal portion of the axillary artery is anatomically fixed and, therefore, susceptible to injury in anterior dislocations. Ischemic injury, including pseudoaneurysm and arterial laceration, is rare but carries marked morbidity if not quickly identified.

Acromioclavicular joint injuries account for more than forty percent of all shoulder injuries. Mild injuries are not associated with any significant morbidity, but severe injuries can lead to significant loss of strength and function of the shoulder. Acromioclavicular injuries may be associated with a fractured clavicle, impingement syndromes, and more rarely neurovascular insults.The AC joint is a diarthrodial joint defined by the lateral process of the clavicle articulating with the acromion process as it projects anteriorly off the scapula. The joint is primarily stabilized by the acromioclavicular ligament, which is composed of an anterior, posterior, inferior, and superior component. Of note, the superior portion of the AC ligament is the most important component for the stability of the AC joint. Supporting structures include two coracoclavicular ligaments (trapezoid and conoid ligaments), which provide vertical stability, as well as the coracoacromial ligament.Patients with an AC joint injury typically present with anterosuperior shoulder pain and will describe a mechanism of injury of blunt trauma to the abducted shoulder or landing on an outstretched arm, suggestive of this type of injury. They may describe pain radiating to the neck or shoulder, which is often worse with movement or when they try to sleep on the affected shoulder. On examination, the clinician may observe swelling, bruising, or a deformity of the AC joint, depending on the degree of injury. The patient will be tender at that location. They may have a restriction in the active and passive range of motion secondary to pain. Piano key sign may be seen, with an elevation of the clavicle that rebounds after inferior compression.Standard X-rays are adequate to make a diagnosis of acromioclavicular joint injury and should be used to evaluate for other causes of traumatic shoulder pain.

Opponens pollicis is a muscle of thenar eminence, it is triangular in shape and lies deep to flexor pollicis brevis and abductor pollicis brevis. It originates from the flexor retinaculum, tubercles of scaphoid and trapezium, abductor pollicis longus tendon.Its insertion is in the radial side of the base of proximal phalanx of thumb. It is supplied by the median nerve (C8, T1). It receives blood supply from superficial arch.It flexes the metacarpal bone medially across the palm, also rotating it medially, causing opposition, the palmar aspect of the terminal segment of thumb contacts the flexor aspects of any other digit.

Abductor digiti minimi is a short intrinsic muscle of the hand. It belongs to the group of muscles collectively called hypothenar muscles due to their acting on the 5th finger. Besides abductor digiti minimi, other hypothenar muscles include flexor digiti minimi brevis and opponens digiti minimi.The main function of abductor digiti minimi involves abduction of the 5th finger, as well as flexion of its proximal phalanx. Along with other hypothenar muscles, this muscle forms the hypothenar eminence on the medial side of the palm.Like other hypothenar muscles, abductor digiti minimi receives nervous supply from the deep branch of the ulnar nerve, derived from root values C8 and T1.Abductor digiti minimi receives arterial blood supply from the palmar branch of ulnar artery, palmar digital artery, as well as branches of the ulnar side of the superficial palmar arch. The venous blood from the muscle is drained via the venous networks of the palm into the deep veins of the arm (vv. ulnares).

Flexor digiti minimi brevis muscle is located on the ulnar side of the palm, lying on the radial border of the abductor digiti minimi. Together with the abductor digiti minimi and opponens digiti minimi muscles, it forms the hypothenar eminence. The muscle is situated inferior and lateral to adductor digiti minimi muscle and superior and medial to opponens digiti minimi muscle. The proximal parts of flexor digiti minimi brevis and abductor digiti minimi muscles form a gap through which deep branches of the ulnar artery and ulnar nerve pass.

Damage to the C5 and C6 nerve roots causes Erb’s palsy. The spinal accessory nerve (CN XI) innervates the trapezius muscle, thus you would not expect this muscle to be impacted. The trapezius is a muscle that runs from the base of the neck across the shoulders and into the centre of the back.

Extensor digitorum is a long muscle located in the posterior compartment of the forearm. Together with the extensor carpi ulnaris and extensor digiti minimi, extensor carpi radialis longus and brevis as well as the brachioradialis, it belongs to the group of superficial extensors of the forearm. These muscles can be easily palpated in the lateral aspect of the posterior forearm, especially during the extension of hand when they are contracted.Extensor digitorum runs from the lateral epicondyle of humerus to the medial four phalanges of the hand. In this way, it generates the pull for the extension of the four medial fingers in their metacarpophalangeal and both interphalangeal joints. Extensor digitorum also participates in the extension of the wrist.Extensor digitorum is innervated by posterior interosseous nerve which is a continuation of a deep branch of radial nerve (root value C7 and C8).Extensor digitorum is vascularized by the branches of three different arteries: (1) posterior interosseous artery, (2) radial recurrent artery, and (3) anterior interosseous artery. Anterior and posterior interosseous arteries are the branches of the common interosseous artery that arises from the ulnar artery. The radial recurrent artery is a branch of the radial artery.

The medial half of the flexor digitorum profundus is innervated by the ulnar nerve. Paralysis of this muscle results in loss of flexion at the distal interphalangeal joint of the ring and little finger. Flexion at the proximal interphalangeal joint is preserved as this is a function of the flexor digitorum superficialis which is innervated by the median nerve. The ulnar nerve is not correct as ulnar nerve injury at the wrist would not affect the long flexors, and the injury must have been more proximal.

The coracobrachialis muscle is innervated by the musculocutaneous nerve (C5-C7) a branch of the lateral cord of the brachial plexus.

Pectoralis minor is a thin, triangular muscle that is situated in the upper chest. It is thinner and smaller than pectoralis major. It is innervated by the medial pectoral nerve.The origin of pectoralis minor is the 3rdto the 5thribs, near the costal cartilages. It inserts into the medial border and superior surface of the coracoid process of the scapula.The main action of pectoralis minor is to draw the scapula inferiorly and anteriorly against the thoracic wall. This serves to stabilise the scapula.

All of the muscles in the anterior forearm are innervated by the median nerve, except for the flexor carpi ulnaris and the medial half of the flexor digitorum profundus which are innervated by the ulnar nerve.

Pronator teres syndrome (PTS) is caused by a compression of the median nerve (MN) by the pronator teres (PT) muscle in the forearm. The median nerve, C6 and C7, innervates the pronator teres.

Extensor indicis is a narrow, elongated muscle found in the posterior compartment of the forearm. It belongs to the deep extensors of the forearm, together with supinator, abductor pollicis longus, extensor pollicis longus, and extensor pollicis brevis muscles. It lacks the juncturae tendinum, which connects the extensor digitorum on the dorsal aspect of the hand.Extensor indicis can be palpated by applying deep pressure over the lower part of the ulna while the index finger is extended. The main function of extensor indicis involves the extension of the index finger at the metacarpophalangeal and interphalangeal joints. As the index finger is one of the few fingers that have their own separate extensor muscle, it is able to extend independently from other fingers. Additionally, extensor indicis muscle produces a weak extension of the wrist.Extensor indicis receives its nervous supply from posterior interosseous nerve, a branch of the radial nerve derived from spinal roots C7 and C8. The skin overlying the muscle is supplied by the same nerve, with fibres that stem from the spinal roots C6 and C7.The superficial surface of the extensor indicis receives arterial blood supply from posterior interosseous branch of the ulnar artery, whereas its deep surface receives blood from perforating branches of the anterior interosseous artery.

The majority of extensor carpi radialis longus originates from the lateral supracondylar ridge of humerus (distal third) and anterior aspect of the lateral intermuscular septum of the arm. A small portion of its fibres originate from the common extensor tendon attached to the lateral epicondyle of humerus. The fibres unite into a muscle belly which extends approximately to the middle of the forearm. The muscle belly is then replaced by a flat tendon that travels distally along the lateral surface of the radius, together with the tendon of extensor carpi radialis brevis. Both tendons course towards the radial styloid process, deep to the tendons of abductor pollicis longus and extensor pollicis brevis muscles. Proximal to the wrist, the tendons of extensor carpi radialis longus and brevis pass behind the radial styloid process within a common synovial sheath and continue along the radial groove deep to the extensor retinaculum of the wrist. At this level, the tendon of extensor carpi radialis longus is crossed by the tendon of extensor pollicis longus, after which it inserts on the posterior aspect of the base of the second metacarpal bone. Some tendon slips can insert into the first and third metacarpal bones.Extensor carpi radialis longus receives innervation from the radial nerve, with contributions mainly from spinal nerves C5-C8. The radial nerve is a branch of the brachial plexus.Extensor carpi radialis longus receives blood supply mainly from the radial artery. It directly supplies the distal part of the muscle, while the rest of the muscle receives blood from one of its radial recurrent branches. The brachial artery also supplies a small portion of the muscle via the radial collateral artery.Extensor carpi radialis longus primarily acts on the wrist joint to produce two major actions: (1) wrist extension by working synergistically with extensor carpi radialis brevis and extensor carpi ulnaris, and (2) hand abduction (radial deviation), with the help of flexor carpi radialis.

The glenohumeral joint possesses the capability of allowing an extreme range of motion in multiple planes.Flexion – Defined as bringing the upper limb anterior in the sagittal plane. The usual range of motion is 180 degrees. The main flexors of the shoulder are the anterior deltoid, coracobrachialis, and pectoralis major. Biceps brachii also weakly assists in this action.Extension—Defined as bringing the upper limb posterior in a sagittal plane. The normal range of motion is 45 to 60 degrees. The main extensors of the shoulder are the posterior deltoid, latissimus dorsi, and teres major.Internal rotation—Defined as rotation toward the midline along a vertical axis. The normal range of motion is 70 to 90 degrees. The internal rotation muscles are the subscapularis, pectoralis major, latissimus dorsi, teres major, and the anterior aspect of the deltoid.External rotation – Defined as rotation away from the midline along a vertical axis. The normal range of motion is 90 degrees. Primarily infraspinatus and teres minor are responsible for the motion.Adduction – Defined as bringing the upper limb towards the midline in the coronal plane. Pectoralis major, latissimus dorsi, and teres major are the muscles primarily responsible for shoulder adduction.Abduction – Defined as bringing the upper limb away from the midline in the coronal plane. The normal range of motion is 150 degrees. Due to the ability to differentiate several pathologies by the range of motion of the glenohumeral joint in this plane of motion, it is essential to understand how different muscles contribute to this action.

Brachioradialis is innervated by the radial nerve (from the root values C5-C6) that stems from the posterior cord of the brachial plexus.

Extensor carpi ulnaris is a fusiform muscle in the posterior forearm. It spans between the elbow and base of the little finger. This muscle belongs to the superficial forearm extensor group, along with anconaeus, brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum and extensor digiti minimi muscles.Like all the muscles of this compartment, extensor carpi ulnaris works as an extensor of the wrist. Moreover, due to its specific course, this muscle also acts to adduct the hand.Extensor carpi ulnaris is innervated by the posterior interosseous nerve (C7, C8), a branch of the deep division of the radial nerve. The radial nerve stems from the posterior cord of the brachial plexus.Blood supply to the extensor carpi ulnaris muscle is provided by branches of the radial recurrent and posterior interosseous arteries, which stem from the radial and ulnar arteries, respectively.

The biceps brachii muscle is one of the chief muscles of the arm. The origin at the scapula and the insertion into the radius of the biceps brachii means it can act on both the shoulder joint and the elbow joint, which is why this muscle participates in a few movements of the arm. It derives its name from its two heads which merge in one unique distal body, defining the unusual structure of the muscle.The biceps brachii muscle is supplied by the musculocutaneous nerve (C5-C6), a branch of the brachial plexus.Arterial supply to the biceps brachii muscle varies considerably, coming from up to eight vessels originating from the brachial artery in the middle third of the arm.In the shoulder joint both muscle heads partially enforce opposite movements. The long head pulls the arm away from the trunk (abduction) and turns it inwards (inward rotation) whereas the short head pulls the arm back towards the trunk (adduction). When both heads contract simultaneously it leads to an arm bend (flexion). In the elbow joint the muscle bends the forearm (flexion) and rotates it outwards (supination). The supination is most powerful in a flexed elbow. In addition to the movement functions, the biceps has the important task to support the humeral head within the shoulder joint. Its antagonist is the triceps brachii in the posterior compartment of the arm.

Damage to the axillary nerve will result in loss of abduction past about 15 degrees and weakness of lateral rotation due to paralysis of the deltoid and teres minor and loss of sensation over the regimental badge area on the upper lateral arm. The axillary nerve is most likely injured in fracture of the surgical neck of the humerus due to its course where it winds around this region together with the posterior humeral circumflex vessels.

According to various studies, the frequency of acute nerve damage associated with supracondylar humeral fractures in children ranges from 10% to 20%. Median nerve injury and anterior interosseous nerve injury are the most common consequences. Damage to this nerve indicated weakening or abnormal extension of the index finger’s distal interphalangeal joint and the thumb’s interphalangeal joint. The absence of sensibility is a distinguishing attribute. A surgical neck humerus fracture may cause injury to the axillary nerve. A midshaft humerus fracture might cause injury to the radial nerve. A medial epicondylar fracture might cause injury to the ulnar nerve.

The radial artery lies lateral to the large tendon of the flexor carpi radialis muscle and anterior to the pronator quadratus at the distal end of the radius. The flexor carpi radialis muscle is used as a landmark in locating the pulse.

Extensor pollicis longus is part of the deep extensors of the forearm together with extensor pollicis brevis, abductor pollicis longus, extensor indicis and supinator muscles. It is located on the posterior aspect of forearm, extending from the middle third of the ulna, and adjacent interosseous membrane, to the distal phalanx of the thumb.Extensor digitorum is innervated by posterior interosseous nerve which is a continuation of a deep branch of radial nerve (root value C7 and C8).Extensor pollicis brevis receives its blood supply from the posterior interosseous artery and perforating branches of the anterior interosseous artery.The main action of extensor pollicis longus is extension of the thumb at the metacarpophalangeal and interphalangeal joints. Extension at the metacarpophalangeal joint occurs in synergy with extensor pollicis brevis muscle. When the thumb reaches the full extension or abduction, extensor pollicis longus can also assist in adduction of the thumb.

The latissimus dorsi muscle is a broad, flat muscle that occupies the majority of the lower posterior thorax. The muscle’s primary function is of the upper extremity but is also considered to be a respiratory accessory muscle.Latissimus dorsi is a climbing muscle. With the arms fixed above the head, it can raise the trunk upwards, together with the help of pectoralis major. Functionally, the latissimus dorsi muscle belongs to the muscles of the scapular motion. This muscle is able to pull the inferior angle of the scapula in various directions, producing movements on the shoulder joint (internal rotation, adduction and extension of the arm). It is innervated by the thoracodorsal nerve (C6 – C8) from the posterior cord of the brachial plexus, which enters the muscle on its deep surface.