MSK Upper Extremities

• Pectoralis Minor

  • Flat, thin muscle that is deep to the pectoralis major
  • Originates from the anterior surfaces of ribs 3-5
  • Inserts into the coracoid process of the scapula
  • Innervated by medial pectoral nerves
  • Serves to protract and rotate the scapula downward
• Serratus Anterior

  • Fan shaped muscle, lies deep to the scapula
  • Originates from the upper 8 ribs
  • Inserts into the vertebral border of the scapula posteriorly
  • Rotates the scapula upward
  • Prime mover to protract and hold the scapula against the chest wall
  • Muscle that is used in pushing, punching, rowing
  • Innervated by the long thoracic nerve
• Subclavius

  • Found just underneath the clavicle
  • Small cylindrical muscle that extends from the 1st rib to the clavicle
  • Innervated by the nerve to the subclavius
  • Helps to stabilize and depress the pectoral girdle
• Trapezius


  • Diamond shaped muscle
  • Found at the superficial part of the back
  • Most superficial muscle of the posterior thorax
  • Upper fibers, middle fibers, and lower fibers
  • Originates from the occipital bone above the ligamentum nuchae and the spines of C7 and all the thoracic vertebrae
  • Inserts along the acromion of the clavicle and the spine of the scapula
  • Innervated by accessory nerve (CN11)
  • Serves to stabilize, elevate, retract, and rotate the scapula
  • The middle fibers can also adduct the scapula
  • Its most prominent action is to elevate the shoulders/shrug the shoulders
• Levator Scapulae

  • Located at the back end at the side of the neck
  • Deep to the trapezius
  • Strap like in shape
  • Attached to the medial border of the scapulae
  • Innervated by the dorsal scapular nerve
  • Inserted into the medial border of the scapulae
  • Can elevate and adduct the scapulae
• Rhomboids

  • Found on the medial border of the scapulae
  • Just below the levator scapulae (rhomboid minor, smaller and superior)
  • Inserted into the medial border of the scapulae
  • Also innervated by the dorsal scapular nerve
  • If they act together they can also retract the scapula and rotate it downward
• Pectoralis Major

  • Large fan shaped muscle that covers the upper portion of the chest
  • Forms your anterior axillary fold
  • Divided into your clavicular part and your sternal parts, depending on where it's attached
  • Originates from the sternal end of your clavicle, sternum, as well as the cartilage of the the first six ribs
  • Inserts into the area of the greater tuberosity of your humerus
  • Innervated by both your lateral and medial pectoral nerves
  • Pectoralis minor is only innervated by the medial pectoral nerve
  • Pectoralis major is the prime mover for flexion of your shoulder joint
  • Pectoralis major flexes the shoulder joint
  • It can also internally rotate and adduct the shoulder
• Deltoid

  • Makes up the roundness of the shoulder
  • Thick multipennate muscle
  • Common site for intramuscular injections
  • Originates from the lateral third of the clavicle, including the acromion and the spine of the scapula
  • Inserts into the deltoid tuberosity found in the proximal part of the humerus
  • Innervated by axillary nerve
  • Prime mover for shoulder abduction
  • Anterior, middle, and posterior fibers
  • Anterior fibers acting alone can flex and internally rotate the shoulder
  • Posterior fibers acting alone can extend and laterally rotate the shoulder joint
• Latissimus Dorsi

  • Broad, flat, triangular muscle of the lower back in the lumbar region
  • Covered partly at the superior area by the trapezius
  • Contributes to the posterior wall of your axilla
  • Originates via the thoracolumbar fascia into the spines of the lower 6 thoracic vertebrae, the lumbar vertebrae, and the iliac crest
  • It inserts in front of the shoulder joint on the floor of the bicipital groove or the intertubercular groove
  • Action: extend the shoulder joint, and adduct and internally rotate the shoulder joint
  • Swimmer's muscle, hypertrophies
  • Plays an important role in bringing down the arm after a powerstroke
• Teres Major

  • Thick, round muscle, located just inferior to the teres minor
  • Originates at the posterior surface of the scapula at the inferior angle
  • Inserts into the lesser tuberosity of the humerus
  • Innervated by the lower subscapular nerve
  • When it contracts, it extends, internally rotates, and adducts the shoulder joint
  • Synergist of latissimus dorsi
• Rotator Cuff Muscles

  • Supraspinatus
  • Infraspinatus
  • Subscapularis
  • Teres Minor
• Supraspinatus

  • Superior to the spine of the scapula
  • Originates from the supraspinous fossa
  • Insert into the greater tuberosity of the humerus
  • Innervated by the suprascapular nerve
  • Abductor of the shoulder
• Infraspinatus

  • Below the spinous process of the scapula
  • Originates from the infraspinous fossa
  • Insert into the greater tuberosity of the humerus
  • Innervated by the suprascapular nerve
  • Laterally/externally rotate the shoulder joint
• Subscapularis

  • Found on the anterior surface of the scapula on the subscapular fossa
  • Originates from the subscapular fossa
  • Inserts into the lesser tuberosity of the humerus
  • Innervated by both upper and lower subscapular nerves
  • Internally/medially rotates the shoulder joint
• Teres Minor

  • Originates from the lateral border of the posterior/dorsal surface of the scapula
  • Insert into the greater tuberosity of the humerus
  • Innervated by the axillary nerve
  • Laterally/externally rotate the shoulder joint
• Biceps Brachii

  • Innervated by the musculocutaneous nerve
  • Action is to flex the elbow and to supinate the forearm
  • Two heads, short head and long head
  • Short head originates from coracoid process of the scapula
  • Long head originates from supraglenoid tubercle of the scapula
  • Common tendinous insertion: the biceps tendon, which inserts into the bicipital tuberosity/the radial tuberosity found on the radius
• Brachialis

  • Strong muscle that is immediately deep underneath the biceps brachii on the distal part of the humerus
  • Innervated by the musculocutaneous nerve
  • Action is to flex the elbow
  • Originates from the anterior surface of the shaft of the distal humerus
  • Inserts into the coronoid process of the ulna
• Coracobrachialis

  • Small, cylindrical muscle located on the proximal portion of the humerus
  • Originates from coracoid process and inserts into the medial surface of the humeral shaft
  • Innervated by the musculocutaneous nerve
  • Action is to flex the elbow
  • Can flex and adduct the shoulder joint
• Triceps Brachii

  • Large muscle, the only muscle in the post. compartment of the arm
  • Lateral head, long head, medial head
  • All insert by a common tendon into the olecranon process of the ulna
  • Long head originates from the infraglenoid tubercle of the scapula
  • Lateral head originates from the posterior shaft of the humerus
  • Medial head originates from the posterior shaft of the humerus, distal to the radial groove
  • Main action: to extend the elbow joint
  • Innervated by the radial nerve
  • Of all the heads, the medial head is the prime mover/work horse for elbow extension
• Pronator Teres

  • Short muscle
  • Two headed muscle
  • One head originates from medial epicondyle of the humerus
  • The other head originates from the coronoid process of the ulna
  • Pronates the forearm
  • Innervated by the median nerve
• Flexor Carpi Radialis

  • Originates from the medial epicondyle
  • Inserts into the bases of the second and third metacarpals
  • Very powerful flexor of the wrist joint
  • Can also abduct the wrist (radial deviation)
  • Innervated by the median nerve
• Palmaris Longus

  • Thin muscle
  • Common muscle that is not present in 10% of people
  • Small muscle with a long insertional tendon
  • Originates from the medial epicondyle and inserts into the palmar aponeurosis
  • Functions to tense the skin of the palm
  • Improves grip slightly
  • No actual motion for a joint
  • Synergist for some flexion of the wrist or the elbow
  • Commonly used for tendon grafts
• Flexor Carpi Ulnaris

  • Most medial muscle in the superficial group
  • Originates from the medial epicondyle
  • Inserts into the pisiform and hamate as well as the base of the 5th metacarpal
  • Flexes the wrist joint
  • Because of its ulnar location it can also adduct the wrist joint (ulnar deviation)
  • Innervated by the ulnar nerve
• Flexor Digitorum Superficialis

  • Separates into 4 tendons that go to the four fingers (except thumb)
  • Originates from the medial epicondyle
  • Once it becomes a tendon it will individually insert into the fingers (specifically at the bases of the middle phalanges)
• Palmaris longus

  • Thin muscle
  • Common muscle that is not present in 10% of people
  • Small muscle with a long insertional tendon
  • Originates from the medial epicondyle and inserts into the palmar aponeurosis
  • Functions to tense the skin of the palm
  • Improves grip slightly
  • No actual motion for a joint
  • Synergist for some flexion of the wrist or the elbow
  • Commonly used for tendon grafts
• Flexor carpi ulnaris

  • Most medial muscle in the superficial group
  • Originates from the medial epicondyle
  • Inserts into the pisiform and hamate as well as the base of the 5th metacarpal
  • Flexes the wrist joint
  • Because of its ulnar location it can also adduct the wrist joint (ulnar deviation)
  • Innervated by the ulnar nerve
• Flexor digitorum superficialis

  • Separates into 4 tendons that go to the four fingers (except thumb)
  • Originates from the medial epicondyle
  • Once it becomes a tendon it will individually insert into the fingers (specifically at the bases of the middle phalanges)
  • Main action is to flex the finger
  • Specifically the proximal interphalangeal joint (between middle phalanx and proximal phalanx)
  • Innervated by the median nerve
• DEEP MUSCLES OF THE ANTERIOR COMPARTMENT

  • Mostly innervated by the median nerve (anterior interosseous nerve)
• Flexor pollicis longus

  • Pollicis means thumb
  • Partly covered by the fds
  • Lateral and just parallel to the fdp
  • Originates from the anterior surface of the radius
  • Inserts into the thumb (distal phalanx)
  • Action: flexion of the interphalangeal joint of the thumb
  • Innervated by the anterior interosseous branch of the median nerve
• Flexor digitorum profundus


  • Profundus means deep
  • Innervated by the of the median nerve
  • Similar to the fds, divides into 4 distinct tendons going to the 4 fingers
  • The radial/lateral half (those tendons going to the index and middle fingers) innervated by the median nerve (anterior interosseous branch)
  • The ulnar/medial half (ring and little finger) innervated by ulnar nerve
  • Originates from the anteromedial surface of the ulna and the interosseous membrane
  • Inserts far more distal than the fds, inserts into the base of the distal phalanges
  • Action: flexion of the distal interphalangeal joint
  • Joint between the distal phalanx and the middle phalanx
  • Because of the course through the entire finger, it also crosses over the proximal interphalangeal joint
  • It can also aid in the flexion of the proximal interphalangeal joint
  • Only muscle capable of flexing the distal interphalangeal joint
• Pronator quadratus

  • Deepest muscle in the distal forearm
  • A little oblique in orientation
  • Only muscle that arises slowly from the ulna and inserts solely into the radius
  • Pronates the forearm
  • Acts together with the pronator teres
  • Holds the ulna and radius together
  • Innervated by the anterior interosseous branch of the median nerve
• POSTERIOR COMPARTMENT OF THE FOREARM

  • Common origin: lateral epicondyle
  • Common action: extend the wrist
  • Common nerve supply: radial nerve (posterior interosseous nerve/deep motor branch)
• Brachioradialis

  • Innervated by branches coming from the main trunk of the radial nerve
  • Found on the most lateral side of the forearm
  • Forms the lateral boundary of the cubital fossa
  • Originates from the lateral supracondylar ridge of the distal humerus
  • Inserts into the base of the radial styloid
  • Synergist in forearm flexion
  • Best to test when the forearm or the elbow is flexed or in midprone/semipronated
  • Can flex the elbow when your forearm is in a midprone position
• Extensor carpi radialis longus

  • Innervated by branches coming from the main trunk of the radial nerve
  • Parallels the brachioradialis
  • Originates from the lateral supracondylar ridge of the distal humerus
  • Inserts into the base of the 2nd metacarpal
  • Extensor of the wrist joint
  • Can also abduct the wrist joint (Radial deviation)
• Extensor carpi radialis brevis

  • Innervated by the radial nerve (posterior interosseous nerve/deep motor branch)
  • Originates from the lateral epicondyle of the humerus
  • Inserts into the base of the 3rd metacarpal
  • Extends the wrist joint
  • Abducts the wrist joint (radial deviation)
• Extensor digitorum

  • Innervated by the radial nerve (posterior interosseous nerve/deep motor branch)
  • More medial to the ecrb
  • Inserts into the 4 fingers
  • Particularly into the extensor expansions of the 4 fingers
  • Prime action: extend the fingers
• Extensor carpi ulnaris

  • Innervated by the radial nerve (posterior interosseous nerve/deep motor branch)
  • Medial to the ED
  • Most medial muscle in the superficial layer
  • Originates from the lateral epicondyle
  • Inserts into the base of the 5th metacarpal
  • Action: extend the wrist joint and adduct the wrist joint (ulnar deviation)
• DEEP MUSCLES OF THE POSTERIOR COMPARTMENT

  • Common nerve supply: posterior interosseous branch of the radial nerve
• Supinator

  • Most lateral side
  • Deep muscle at the posterior aspect of the elbow
  • Largely concealed by the superficial muscles
  • Originates from the lateral epicondyle
  • Inserts into the proximal end of the radius
  • Supinates the forearm, together with the biceps brachii
• Abductor pollicis longus

  • Originates from the posterior surface of both the radius and the ulna
  • Inserts at the base of the 1st metacarpal and the trapezium
  • Abducts the thumb