Upper Extremity Kinesiology and Biomechanics Review

Flashcards covering kinesiology, functional anatomy, biomechanics, and clinical pathology of the elbow, shoulder, wrist, and hand complexes.

Which three joints comprise the elbow complex?

The humeroulnar, humeroradial, and proximal radioulnar joints.

What two primary anatomical factors provide stability to the elbow?

Bony geometry and ligamentous support.

What type of movement is primarily permitted by the humeroulnar joint?

Flexion and extension.

Which muscle remains consistently active across all forearm pronation activities?

Pronator quadratus.

What injury is the most common cause of a cubitus varus deformity?

A distal humerus fracture.

Which portion of the elbow joint capsule becomes taut during full extension?

The anterior capsule.

Which muscle acts as a dynamic stabilizer of the distal radioulnar joint?

Pronator quadratus.

What condition is defined by an increased carrying angle of $25^\circ$ on the dominant arm?

Cubitus valgus.

When the forearm is flexed to $90^\circ$, which muscle primarily performs supination?

Biceps brachii.

Which muscle serves as the primary initiator of low-load elbow extension?

Anconeus.

In a client with a spinal cord injury lacking triceps function, which muscle is primarily used to achieve compensatory elbow extension during wheelchair pressure relief push-ups?

Pectoralis major.

During forearm rotation, which bone pivots around the other?

The radius pivots around the ulna.

Which muscle is primarily recruited during slow, low-resistance supination such as turning a key?

Supinator.

What general recruitment adaptation occurs in the body when force demand increases?

The body recruits more muscles.

What anatomical feature of the humerus produces the carrying angle of the elbow?

The trochlea extends more distally than the capitulum.

Which muscle is most likely involved when a patient experiences pain during resisted forearm pronation?

Pronator teres.

What role does the triceps brachii play when the biceps brachii acts as a primary supinator to turn a doorknob?

It acts as a synergist by stabilizing the elbow and preventing unwanted flexion.

What principle governs optimal motor unit recruitment during functional upper extremity tasks?

The body recruits single-joint muscles first.

Which forearm rotator is uniaxial and unaffected by the angle of the elbow?

Supinator.

When lowering a grocery bag from a counter by extending the elbow, which muscle controls the descent eccentrically?

Biceps brachii.

What is the recruitment order of the three heads of the triceps brachii against increasing loads?

The medial head is recruited first, followed by the lateral head, and finally the long head.

Which joint represents the sole true bony articulation connecting the upper extremity to the axial skeleton?

Sternoclavicular joint.

Which muscle is NOT a member of the rotator cuff: Supraspinatus, Teres major, Infraspinatus, or Teres minor?

Teres major.

Why is the surgical neck of the humerus clinically significant?

It is a common fracture site.

How is the scapulothoracic articulation classified anatomically?

A pseudo joint.

What is the mechanical definition of a force couple?

Two opposite forces producing rotation around an axis.

Which ligament limits excessive elevation of the clavicle at the sternoclavicular joint?

Costoclavicular ligament.

How do the anterior and posterior deltoid muscles function relative to each other during horizontal shoulder motion?

As antagonists.

A patient using crutches relies heavily on which shoulder structure to maintain trunk elevation?

Scapulothoracic joint.

A client with an infraspinatus tear will experience functional deficits during which activity requiring external rotation?

Brushing their hair.

What displacement does the coracoacromial arch prevent at the shoulder?

Upward humeral displacement.

What combination of movements does the latissimus dorsi produce at the glenohumeral joint?

Extension, adduction, and medial rotation.

Which ligament primarily resists posterior displacement at the sternoclavicular joint during arm cocking?

Anterior sternoclavicular ligament.

Which anatomical structure is commonly referred to as the “rooftop” of the shoulder?

Coracoacromial arch.

Which structure serves as the primary shock absorber of the glenohumeral joint?

The glenoid labrum.

What primary movement does the subscapularis execute at the glenohumeral joint?

Medial rotation.

What is the primary function of the acromioclavicular (AC) joint during arm elevation?

To maintain glenoid alignment with the humeral head.

What are the primary dynamic stabilizing muscles of the glenohumeral joint?

The rotator cuff muscles.

Which segment of the deltoid initiates and assists shoulder flexion?

Anterior deltoid.

What movement is produced by the coordinated activation of all three parts of the deltoid?

Abduction.

Which muscle is responsible for scapular protraction?

Serratus anterior.

What are the normal arthrokinematics of the humeral head during glenohumeral abduction?

The humeral head rolls superiorly and slides inferiorly.

Which muscle acts as a prime mover of the glenohumeral joint without serving as a scapular stabilizer?

Latissimus dorsi.

Which ligament prevents upward displacement of the sternoclavicular joint?

Interclavicular ligament.

What clinical sign typically manifests from weakness or paralysis of the serratus anterior?

Scapular winging.

In addition to the SITS rotator cuff muscles, which two arm muscles provide active glenohumeral joint stabilization?

Biceps and triceps.

Which thumb position is NOT characteristic of the functional resting position of the hand?

Thumb radial abduction.

What functional impairment results from rupture of the flexor tendon annular pulley system?

Bowstringing of tendons and reduced grip strength.

How do intrinsic and extrinsic hand muscles functionally divide labor?

Extrinsic muscles supply power and gross strength, whereas intrinsic muscles execute fine motor adjustments for precision tasks.

Where are the thenar and hypothenar muscle groups positioned on the hand?

The thenar group is located at the base of the thumb, and the hypothenar group is located at the base of the fifth finger.

Which precision grip is considered the least precise?

Lateral pinch grip.

Which flexor tendon pulley is most frequently involved in trigger finger pathology?

A1 pulley.

Inability to hold a water bottle using a cylindrical grasp points to a weakness in which muscle group?

Palmar interossei.

Pain over the lateral epicondyle accompanied by weakened, painful grip is indicative of which condition?

Lateral epicondylitis.

Weakened thumb opposition combined with thenar eminence atrophy signals injury to which peripheral nerve?

Median nerve.

What kinematic movements are produced by the intrinsic lumbrical muscles?

Flexion of the metacarpophalangeal (MCP) joints and extension of the interphalangeal (IP) joints.

Inability to extend the wrist and digits following a midshaft humerus fracture indicates trauma to which nerve?

Radial nerve.

Which wrist extensor muscle assists in holding the wrist in extension when signaling "STOP"?

Extensor digitorum.

Paresthesia and numbness localized to the fifth digit and ulnar aspect of the fourth digit indicate injury to which nerve?

Ulnar nerve.

Which intrinsic muscle group drives digit abduction away from the midline of the hand?

Dorsal interossei.

Inability to flex the index and middle fingers when attempting to close a fist is classic evidence of what nerve lesion?

Median nerve injury.

Which specific joint of the thumb does the extensor pollicis longus primarily extend?

The interphalangeal ($\text{IP}$) joint.

Which muscle pair acts synergistically to produce pure wrist extension without deviation?

Extensor carpi radialis brevis (ECRB) and extensor carpi ulnaris (ECU).

What is the functional relationship between the wrist and the hand?

The wrist provides joint stability, allowing the hand to perform fine motor control.

At what anatomical site is hand sensory evaluation conventionally initiated?

The most distal aspect of the fingers.

Which carpal bone is the most frequently fractured?

The scaphoid.

Which fibrocartilaginous structure separates the distal ulna from the medial carpal bones?

The triangular fibrocartilage complex (TFCC).

What mechanical role does the capitate assume within the carpus?

It acts as the central axis of rotation or “pillar” of the carpal bones.

Which carpal bones articulate directly with the distal articular surface of the radius?

Scaphoid and lunate.

What structural role is served by the 3rd metacarpal in hand architecture?

It serves as the most stable central pillar of the hand.

How many phalanges compose the skeletal framework of the thumb?

$2$ phalanges (proximal and distal).

How are the metacarpophalangeal (MCP) joints structurally classified?

Condyloid joints possessing $2$ degrees of freedom.

What anatomical connections characterize the extrinsic wrist ligaments?

They connect the radius, ulna, or metacarpals to the carpal bones.

What structure constitutes the roof of the carpal tunnel?

The flexor retinaculum (transverse carpal ligament).

What is the primary biomechanical purpose of the volar (palmar) plates at the finger joints?

To prevent joint hyperextension and provide structural reinforcement.

Which bony landmarks are linked by the deep transverse metacarpal ligaments?

The heads of metacarpals $2\text{--}5$.

What functional hand task is enhanced by the sesamoid bone mechanism of the thumb?

Pinch precision.