Elbow/Forearm Complex: Kinesiology

bones of the elbow and forearm

humerus, ulna, radius

joints of the elbow and wrist

-humero-ulnar
-humero-radial
-proximal radio-ulnar
-distal radio-ulnar

the trochlea is convex/concave (choose 1)

concave

the capitulum is convex/concave (choose 1)

convex

carrying angle of the humerus

lateral lip of the trochlea

the __________ takes on the most shock absorption (about 60-80%) of forearm compression/forces

radius

________ is the articulating point for the elbow

ulna

________ is the articulating point for the wrist

radius

normal (average) cubital valgus

13 degrees (+ or - 6 degrees)

excessive cubital valgus

> 20 degrees

cubitus varus

-5 degrees --> "gunstock deformity"
-forearm deviates toward midline

typically, "carrying angle" is greater on the ____________ arm

dominant

why women typically have larger carrying angles (2 degrees)

due to child-bearing. wider hips (wider carrying angles) required

joint capsule of the elbow encloses..

humero-ulnar joint, humero-radial joint, and proximal radio-ulnar joint

elbow joint capsule

-reinforced anteriorly by oblique bands of fibrous tissues

-contains a synovial membrane

-strengthened by collateral ligaments

medical collateral ligament (MCL) of ulna --> anterior fibers

anterior fibers are strongest and stiffest, provides most of the resistance against valgus forces

medical collateral ligament (MCL) of ulna --> posterior fibers

less defined and are simply thickenings of the posterior-medial capsule

medical collateral ligament (MCL) of ulna --> transverse fibers

do not provide significant articular stability due to its attachment points- but, adds a bit of stability

the wrist _______ and _______ muscle groups also resist valgus stresses at the elbow. ________ leads the charge

-flexor and pronator
-flexor carpi unlaris

_______ nerve provides stability to the elbow as well

ulnar

when the MCL is most at risk for injury in a baseball pitchers swing

between the cocking phase and acceleration (swing) phase

lateral to medial force

valgus

medial to lateral force

varus

lateral collateral ligament (LCL) of ulna

originates on the lateral epicondyle and immediately splits into 2 fiber bundles

radial collateral ligament (of LCL)

fans out and blends with the annular ligament

lateral (ulnar) collateral ligament

attaches to the supinator crest of ulna; primary lateral elbow stabilizer

role of the nervous system

multiple structures and nervous mechanoreceptors serve an integral role in the preservation and protection of the elbow joint

80 degrees of elbow flexion

-lowest amount of intra articular pressure
-less joint compression force
-less symptom elevation

intra-articular pressure of the elbow increases/decreases in elbow flexion. (choose 1)

decreases

elbow is a ______ joint

hinge (modified)

elbow has ________ degrees of freedom

1

elbow works primarily in the ______ plane

sagittal

the part of the humerus that defines our cubital valgus (or carrying angle)

medial lip of trochlea

humero-ulnar joint type

hinge

humero-radial joint type

condyloid (pivot)

radio-ulnar joint type

pivot joint

humeroulnar open packed position

70 degrees flexion, 10 degrees supination

humeroradial open packed position

full extension, full supination

proximal radioulnar open packed position

70 degrees flexion, 35 degrees supination

distal radioulnar open packed position

10 degrees supination

stability of the joints are derived from __________ tissue

periarticular

humeroulnar closed pack position

extension

humeroradial closed pack position

elbow flexed to 90 degrees, forearm supinated 5 degrees

proximal radioulnar closed pack position

5 degrees supination

distal radioulnar closed pack position

5 degrees supination

ACL rupture typically occurs in closed/open packed position (choose 1).

closed packed

capsular patterns (pattern of ROM loss) --> humeroulnar joint

flexion > extension

capsular patterns (pattern of ROM loss) --> humeroradial joint

extension > supination > pronation

capsular patterns (pattern of ROM loss) --> proximal radioulnar joint

supination > pronation

capsular patterns (pattern of ROM loss) --> distal radioulnar joint

full range of movement with pain at extremes of rotation

active motions of the elbow

flexion and extension

passive motions of the elbow

varus translations, valgus translations, axial rotation (to some extent)

joint mobilizations occur in the direction of the roll/slide (choose 1)

slide

"normal" ROM

standard ROM for MOST of the population

"functional arc" of motion

-the ROM through which most functional activities are performed daily
-30-130 degrees of flexion for the elbow

of pathologies to musculature, we notice that UE/LE are most debilitating to quality of life (choose 1)

UE

articulation of the humero-radial joint

between the concave fovea of the radial head and the convex capitulum of the humerus

in flexion, the contracting muscles pull the radial fovea firmly _____________ the capitulum

against

the humero-radial joint provides ________% of stability to the forearm articulations in the frontal plane

50

radius rolls and slides in a non-pathologic elbow joint (T/F)

false

function of the interosseous membrane

-binds the radius and ulna together
-serves as the attachment site for several extrinsic muscles of the hand
-transmits forces proximally throughout the upper limb

the interosseous membrane transmits approximately __________% of the compression force that crosses the wrist directed through the radiocarpal joint

80

primary load bearing structure of the forearm

radius

the remaining 20% of force (not transmitted through the interosseous membrane) crosses the medial side of the wrist through the soft tissues of the ____________ space

ulnocarpal

compression forces are associated with _______ kinetic chain (i.e. tension being loaded into interosseous membrane)

closed

distracting forces are associated with ______ kinetic chain (i.e. holding your backpack, causes the radius to pull away from capitulum and causes slackening in interosseous membrane)

open

this ligament holds the head of the radius against the ulna

annular ligament

radial head is held against the proximal ulna by a ________________, formed by the annular ligament and radial notch

fibro-osseous ring

elbow capsule is thinner/thicker than the GH capsule (choose 1)

thinner

would varus or valgus force compromise the LCL?

varus

________ ligament attaches proximal head of ulna to the head of the radius

quadrate

at the distal radio-ulnar joint, the head of the ulna is convex/concave (choose 1)

convex

articular disc of the distal radio-ulnar joint; occupies most of the "ulnocarpal space"

triangular fibrocartilage complex (TFCC)

primary stabilizer of the distal radio-ulnar joint

TFCC

_______________ appears in the case of a TFCC tear or injury

hypermobility

motions of the proximal and distal radio-ulnar joint

supination and pronation

functional arc of the elbow

50/50

normal arthro arc of the elbow (supination/pronation)

80/80

normal surgeons arc of the elbow

70/85

in isolated pronation or isolated supination the ________ remains visually stationary, allowing the _______ to rotate and pivot upon the humero-ulnar joint

ulna = stationary, radius = rotate

"screw home" mechanism of elbow

-as we move into terminal elbow extension, we get some transverse rotation of ulna and radius

-get even more osseous interlocking (olecranon tucked into olecranon fossa) and get more stability from joint

joint where you will see the most "wear and tear" as we age

humero-radial

nerves providing motor and sensory innervation to the muscles, ligaments, joint capsules and skin of elbow/forearm, wrist and hand?

musculocutaneous, radial, median, ulnar

sensory innervation of humero-ulnar joint

C6-C8

sensory innervation of the humero-radial joint

C6-C8

sensory innervation of proximal radio-ulnar joint

C6-C7

sensory innervation of distal radio-ulnar joint

C8

muscles that attach distally on the ________ may flex or extend the elbow, but possess no ability to pronate or supinate the forearm

ulna

muscles that attach distally on the _______ may flex or extend the elbow AND have the potential to pronate or supinate the forearm

radius

muscles that primarily act upon the wrist also cross the _________ joint

elbow

primary elbow flexors

biceps brachii, brachialis, brachioradialis

secondary elbow flexors

pronator teres, FCU, FCR, FDS, FDP, and PL

muscle with the greatest PCSA in the arm?

brachialis

muscle with the most forceful contraction of the arm?

biceps brachii

factors to consider when determining the point at which a muscle produces its GREATEST force

-angle of max normal force production
-length tension relationship (degree of elbow flexion)
-maximum internal/effort lever arm

primary elbow extensors

triceps brachii and anconeus

primary forearm supinators

supinator, biceps brachii

secondary forearm supinators

radial wrist extensors,
extensor pollicis longus,
extensor indicis,
brachioradialis

primary supinating muscle of the forearm

biceps brachii

muscle recruited FIRST by the nervous system for forearm supination

supinator