Upper Extremity Kinesiology: Shoulder, Elbow, Forearm, and Brachial Plexus

Comprehensive practice flashcards detailing the functional anatomy, kinesiology, bony landmarks, musculature, joint mechanics, and clinical conditions of the shoulder, elbow, forearm, and brachial plexus.

Scapulothoracic Joint

An atypical structural and functional joint formed by the anterior surface of the scapula gliding over the posterior thoracic cage, permitting elevation, depression, abduction, adduction, internal/external rotation, upward/downward rotation, and anterior/posterior tilt.

Sternoclavicular (SC) Joint

A triaxial saddle or ball-and-socket joint connecting the medial end of the clavicle to the manubrium of the sternum, permitting clavicular elevation, depression, protraction, retraction, and anterior and posterior rotation.

Acromioclavicular (AC) Joint

A biaxial gliding joint connecting the lateral acromial end of the clavicle to the acromion process of the scapula, allowing anterior/posterior and superior/inferior gliding.

Glenohumeral Joint

A triaxial ball-and-socket joint formed by the head of the humerus articulating with the glenoid cavity (fossa) of the scapula, permitting flexion, extension, abduction, adduction, internal rotation, external rotation, and horizontal abduction/adduction.

Scapulohumeral Rhythm

The coordinated kinematic relationship where, beyond $30^\circ$ of shoulder elevation, the scapula and humerus move at a $1:2$ ratio; full $180^\circ$ shoulder flexion or abduction requires approximately $60^\circ$ of scapular upward rotation and $120^\circ$ of humeral elevation.

Rotator Cuff

A dynamic stabilizing musculotendinous cuff surrounding the glenohumeral joint composed of four muscles: supraspinatus, infraspinatus, teres minor, and subscapularis (SITS).

Supraspinatus

A rotator cuff muscle originating in the supraspinous fossa of the scapula that abducts the humerus; it is the most commonly injured and torn rotator cuff tendon.

Subscapularis

An anterior rotator cuff muscle originating in the subscapular fossa that produces internal (medial) rotation of the humerus.

Infraspinatus and Teres Minor

Posterior rotator cuff muscles that externally (laterally) rotate the humerus, essential for activities such as swinging a racket or reaching behind the head.

Teres Major

A scapulohumeral muscle that adducts, extends, and internally rotates the humerus, active during tasks such as pulling an object or reaching into a back pocket.

Serratus Anterior

An axioscapular muscle that protracts the scapula, assists with upward rotation, and secures the medial border of the scapula flat against the thoracic wall.

Scapular Winging

A clinical presentation where the medial border of the scapula lifts away from the posterior rib cage, resulting from serratus anterior weakness or paralysis due to long thoracic nerve injury.

Subacromial Impingement

Pathological compression of the soft tissues (such as the subacromial bursa and supraspinatus tendon) located within the subacromial space between the acromion and humeral head.

Glenohumeral Subluxation

A condition where the humeral head partially dislocates inferiorly from the glenoid cavity due to muscular weakness, paralysis, or flaccidity (frequently following a stroke with hemiparesis), placing painful traction on the joint capsule.

GivMohr Sling

A specialized supportive dynamic orthosis designed to support the flaccid upper extremity, relieve gravitational downward strain on the glenohumeral joint capsule, and address shoulder subluxation after stroke.

Upper Crossed Syndrome

A postural pattern of muscle imbalance characterized by forward head posture, tight/short upper trapezius, levator scapulae, and pectorals, coupled with weak/long deep neck flexors, rhomboids, serratus anterior, and lower/middle trapezius.

SLAP Tear

Superior Labrum Anterior to Posterior lesion; an injury involving detachment or tearing of the superior portion of the glenoid labrum where the long head of the biceps brachii tendon attaches.

Humeroulnar Joint

A uniaxial hinge joint formed by the trochlea of the humerus and the trochlear notch of the ulna that provides high bony congruity and limits movement strictly to flexion and extension.

Humeroradial Joint

A biaxial modified hinge joint formed between the capitellum of the humerus and the head of the radius that permits elbow flexion and extension, as well as radial head rotation during pronation and supination.

Proximal Radioulnar Joint

A uniaxial pivot joint where the circumference of the radial head rotates within the radial notch of the ulna, producing forearm pronation and supination.

Annular Ligament

A strong fibrous band that wraps around the head of the radius to retain it within the radial notch of the ulna while preventing inferior displacement during rotation.

Ulnar Collateral Ligament (UCL)

A triangular ligament extending from the medial epicondyle of the humerus to the coronoid process and olecranon that prevents excessive valgus stress at the elbow.

Radial Collateral Ligament (RCL)

A stabilizing ligament extending from the lateral epicondyle to the annular ligament of the radius that prevents excessive varus angulation at the elbow.

Carrying Angle

The normal physiological valgus angulation formed between the longitudinal axes of the humerus and forearm in full extension, measuring $5^\circ\text{–}10^\circ$ in men and $10^\circ\text{–}15^\circ$ in women.

Cubitus Varus

An abnormal elbow deformity in which the forearm deviates medially toward the midline of the body relative to the long axis of the humerus.

Cubitus Valgus

An abnormal elbow deformity in which the forearm deviates laterally away from the midline of the body beyond the normal physiological carrying angle.

Interosseous Membrane

A broad, fibrous connective tissue sheet extending between the interosseous borders of the radius and ulna that transmits mechanical force from the radius to the ulna, protecting the humeroradial joint from excessive compression.

Brachialis

A deep anterior arm muscle originating on the distal half of the anterior humerus and inserting onto the coronoid process and ulnar tuberosity that functions as a pure flexor of the elbow regardless of forearm rotation.

Brachioradialis

A superficial forearm muscle running from the lateral supracondylar ridge of the humerus to the radial styloid process that flexes the elbow joint and rotates the forearm to neutral from full pronation or supination.

Anconeus

A small triangular muscle located at the posterolateral elbow extending from the lateral epicondyle to the olecranon process that functions as a weak elbow extensor.

Pronator Quadratus

A deep, flat quadrangular muscle of the distal anterior forearm that actively pronates the forearm during all pronation movements, regardless of elbow flexion position.

Cubital Tunnel Syndrome

A peripheral compressive neuropathy of the ulnar nerve behind the medial epicondyle of the humerus, leading to numbness, paresthesia, and tingling along the ring and small fingers.

Lateral Epicondylosis

Also known as tennis elbow; a cumulative trauma disorder characterized by chronic pain, tenderness, and degeneration at the common extensor tendon origin on the lateral epicondyle.

Medial Epicondylosis

Also known as golfer's elbow; a cumulative trauma disorder caused by repetitive strain and tissue breakdown at the common flexor-pronator tendon origin on the medial epicondyle.

Scapular Depression Transfer

A functional transfer method where an individual with absent active triceps extension uses closed-chain scapular depression (via the latissimus dorsi, lower trapezius, and pectoralis minor) to lift the pelvis and body off a seating surface.

Brachial Plexus

A complex network of somatic nerves formed by the anterior (ventral) rami of cervical and thoracic spinal nerves $C5\text{–}T1$ that supplies sensory and motor innervation to the upper limb.

Scalene Interval

The anatomical space between the anterior scalene and middle scalene muscles through which the ventral rami roots of the brachial plexus pass as they emerge from the cervical spine.

Trunks of the Brachial Plexus

The three anatomical bundles formed directly by the roots: the Upper trunk ($C5\text{–}C6$), Middle trunk ($C7$), and Lower trunk ($C8\text{–}T1$).

Cords of the Brachial Plexus

The three nerve groupings (lateral, medial, and posterior) formed by regrouped anterior and posterior divisions, named according to their anatomical location relative to the axillary artery.

Lateral Cord

The cord of the brachial plexus formed by the union of the anterior divisions of the upper and middle trunks, lying lateral to the axillary artery.

Medial Cord

The cord of the brachial plexus formed by the anterior division of the lower trunk, lying medial to the axillary artery.

Posterior Cord

The cord of the brachial plexus formed by the convergence of the posterior divisions of all three trunks (upper, middle, and lower), lying posterior to the axillary artery.

Musculocutaneous Nerve

A terminal branch of the lateral cord ($C5\text{–}C7$) that supplies motor innervation to the anterior compartment flexor muscles of the arm (coracobrachialis, biceps brachii, and brachialis).

Axillary Nerve

A terminal branch from the posterior cord ($C5\text{–}C6$) that innervates the deltoid and teres minor muscles and provides sensory coverage over the lateral shoulder.

Radial Nerve

A major terminal branch of the posterior cord ($C5\text{–}T1$) that provides motor innervation to all extensor muscles of the arm and forearm and skin on the dorsal limb.

Median Nerve

A terminal branch formed by contributions from both the lateral and medial cords ($C5/C6\text{–}T1$) that innervates most forearm flexors, forearm pronators, and thenar intrinsic hand muscles.

Ulnar Nerve

A terminal branch of the medial cord ($C8\text{–}T1$, with occasional $C7$ contribution) providing motor innervation to the majority of intrinsic hand muscles and medial wrist/digit flexors.

Long Thoracic Nerve

A motor nerve arising directly from the ventral rami roots of $C5$, $C6$, and $C7$ that descends along the lateral chest wall to innervate the serratus anterior.

Thoracodorsal Nerve

A collateral branch arising from the posterior cord ($C6\text{–}C8$), also known as the middle subscapular nerve, that innervates the latissimus dorsi muscle.

Erb's Palsy

An upper brachial plexus injury resulting from traction or trauma to the $C5\text{–}C6$ nerve roots or upper trunk, frequently occurring during difficult childbirth or lateral head-shoulder distraction falls.

Klumpke's Palsy

A lower brachial plexus injury resulting from traction on the $C8\text{–}T1$ nerve roots or lower trunk (such as when grabbing an overhead object while falling), leading to paralysis of the intrinsic muscles of the hand.

Radial Nerve Palsy

A peripheral neuropathy caused by damage or compression of the radial nerve, characterized clinically by an inability to actively extend the wrist and fingers, known as wrist drop.

Thoracic Outlet Syndrome (TOS)

A constellation of symptoms caused by compression of the brachial plexus and/or subclavian vessels within the thoracic outlet between the clavicle and the first rib, the scalene triangle, or beneath the pectoralis minor.