<5 deg

>15 deg

-15 deg

Carrying angle is present during

Carrying angle is absent during

There is slight increase in the angle in the dominant arm compared to the nondominant arm

Carrying angle increaes until around age 14 or 15, when epiphyseal ______ occurs, then decrease slightly but becomes more consistent after age ____

Carrying angle is usually about _____ deg in full extension, with a range of ______

An increased carrying angle beyond the normal range, which may be abnormal, esp if unilateral

The carrying angle typically disappears when the forearm is supinated and flexed against the humerus

The carrying angle disappears at flexion beyond 30 deg, as found by

The configuration of the trochlear groove determines the pathway of the forearm during flexion and extension

Trochlear groove common configuration: ulna is guided medially from extension to flexion, so in full flexion the forearm aligns with humerus

Trochlear groove config: in extension, forearm moves _______ to a positional slightly ______ to the axis of the humerus

Different configurations of the trochlear groove can lead to variations in the forearm’s path during flexion, causing it to rest either medially or laterally to the humerus in full flexion

Factors affecting motion of elbow joint

Passive flexion typically has a smaller range than an active motion due to muscle bulk limiting approximation between the forearm and humerus

Active flexion range

Passive flexion range

Flexion ROM is greater when the forearm is supinated compared to pronation or a neutral position

Higher BMI may limit elbow ROM. Studies show an increase of 2-3 deg for each z-score increase in BMI

Muscles crossing both the elbow and shoulder, such as the brachioradialis and brachialis, may restrict elbow motion when both jts attempt full ROM simultaneously

Joint surface configuration, ligaments and joint capsule all contribute to limiting ROM while providing stability

Closed pack position of humeroulnar jt

Closed pack position humeroulnar jt:

Valgus resistance in closed pack position

Varus resistance in close pack position

In full extension, resistance to joint distraction is provided by soft tissue structures, particularly the

Limits the extremes of flexion

At 90 degrees flexion, the anterior lart of the MCL provides primary resistance to both distraction and valgus stress

Varus stress at 90 deg flexion

EMG

Used to monitor the electrical activity produced by the firing of motor units

Helps determine the relative proportion of motor units firing in a muscke during a specific contraction

EMG can identify muscle activation patterns of agonists and antagonsists

Elbow flexors

Tasks requiring stability

Uniarticular muscles

Biarticular muscles

Concave, located on the lat aspect of proximal ulna and mi ed with articular cartilage

Encircles the radial head, lined with articular cartilage and attaches to the radial notch’s anterior and posterior edges

Connects to the ulna, capsule and collateral ligaments

Collagen-rich, mostly avascular and articulates with ulnar head and carpal bones

PRUJ ARTICULATING SURFACES

DRUJ ARTICULATING SURFACES

PRUJ DISC SURFACES

DRUJ DISC SURFACES

PRUJ and DRUJ are mechanically linked, with motion in one joint affecting the other

Joints surfaces of radioulnar is optimal in maximal pronation/supination, with minimal contact in neutral position

Radius crosses over ulna

Radial head spinning within annular ligament and radial notch

Ulnar head rests against the palmar aspect of the ulnar notch

Subluxation/dislocation of the radial head from the annular ligament

Limits the spin of the radius

Taut in supination

Runs from ulna to radius

Forms 4/5 of ring

No direct attachment to the radius

Attached to ulna and rotates around the radiak head and attaches back to the ulna

Found anteriorly

Found posteriorly

2 divisions of radioulnar ligament

Stabilizes the PRUJ and DRUJ

Interosseous membrane structure

Encircles four-fifths of the radial head, covered with cartilage, blending with joint capsule and reinforced by LCL

Connects the ulna’s radial notch to the neck of the radius, reinforcing the inferior joint capsule and limiting radial head spin during forearm rot

Extends from below the ulna’s radial notch to the bicipital tuberosity of radius

its function may be to prevent separation of the radius and ulna

Thick, collagen rich, maintains spacing between radius and ulna during rotation

Thin, soft, adjacent to the central band

Runs counter to central band, from the ulna to the middle radius

Runs from the ulnar notch of the radius to the ulnar fovea and styloid process

Remains taut during rotation, preventing radial-ulnar separation and helps transfer wrist loads to the forearm

Primary muscles for pronation and supination

Anconeus may also assist in supination and pronation

Ulnar head moves distally and dorsally

Ulanr head moves proximally and medially

The axis of motion for pronation and supination is a longitudinal axis extending from the center of the radial head to the center of the ulnar head

The motion of proximal ulna is less in magnitude compared to that of the radius and is opposite in direction

Elbow injuries

Pronator teres

Pronator quadratus

Supinator muscle acts alone during unresisted slow supination in any elbow or forearm position. But it cannot act alone during fast supination with the elbow extended

Supination torque increaes as the forearm moves into pronation, peaking at about 20 deg of pronation

Biceps brachii is involved during resisted supination or fast supination with the elbow flexed

Maximum torque values for supinators are found in the ________ deg range of pronation

Isometric testing shows that pronators are stronger than supinators, highlighting the functional distinctions between these muscle groups

DRUJ stability muscular support

taut in pronation

Taut in supination

Prevent separation of ulna and radius, allowing about 5 mm of movement before resisting distraction

Stabilizes the DRUJ, taut in pronation and loose in supination, protecting the ulnar head

Cushions compressive forces from the carpal to the ulna and stabilizes the ulnar side, bearing strain based on FA position

Elbow stabilization muscles

Elbow flexion ROM

Forearm rotation

The diarthrodial joint of the radioulnar system allows for pronation and supination, enhancing hand mobility but compromising stability. Muscles like the extensor carpi radialis brevis and extensor carpi ulnaris attach at the distal humerus, creating a functional link between the elbow, wrist, and hand.

Aging reduces pennation angles and fascicle lengths, leading up to 50% muscle function loss. Passive stretching can counter this by increasing fascicle length

Older adults: less type 2 fibers, same type 1 fiber percentage

Muscle mass and contraction tyoe influence performance loss, with isometric contractions being least affected