medial portion of trochlea projects more distally than the lateral portion - results in valgus angulation of the forearm - combo of shoulder ER, elbow EX, and forearm supination - Fx: allows a person to carry objects away from side of thigh - Angle varies 8-15 degrees

Lec 11 Elbow Complex Flashcards by Elizabeth Diaferia

Joints of the elbow complex

humeroulnar
humeroradial
prox. and dist. radioulnar

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Articulation of Humeroulnar

Trochlear notch of ulna

Trochlea of humerus

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Articulation of Humeroradial

Head of radius

Capitulum of humerus

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Elbow joint type and DOF

Modified hinge

1 DOF

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Joint of elbow complex includes:

elbow and proximal radioulnar joint enclosed in a single joint capsule
large, loose and weak anteriorly and posteriorly
contains folds that can expand to allow for a full ROM
Fat pads
reinforced laterally by collateral ligaments

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Carrying angle

medial portion of trochlea projects more distally than the lateral portion

results in valgus angulation of the forearm
combo of shoulder ER, elbow EX, and forearm supination
Fx: allows a person to carry objects away from side of thigh
Angle varies 8-15 degrees

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Passive structures of elbow joint ligaments

medial (ulnar) collateral ligament

Lateral collateral ligament complex

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Medial Collateral Ligament

anterior, posterior and transverse parts

stabilizes against valgus torque at elbow
limits extension at end ROM

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Lateral Collateral Ligament complex

stabilizes against varus torque at the elbow and combined varus & supination torques

Lateral (radial) collateral lig
Lateral (ulnar) collateral lig
Annular ligament

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When could extreme valgus-producing force occur?

when trying to catch oneself from a fall

-may result in rupture of MCL and/or compression force within the humeroradial joint

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Is the Humeroradial articulation incongruent or congruent? What position is there no contact between the articulation?

incongruent

- no contact in full extension between surfaces

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Osteokinematics of Humeroulnar (elbow)

Flexion and Extension

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Arthrokinematics of Humeroulnar (elbow)

concave surface of trochlear notch on convex trochlea

flexion: roll anterior, slide anterior
extension: roll posterior, slide posterior

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Elbow joint closed packed position

Humeroulnar and Humeroradial

Humeroulnar: full extension and supination
Humeroradial: 90 degrees elbow flexion and 5 degree supination

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Elbow joint open packed position

Humeroulnar and Humeroradial

Humeroulnar: Flexed 70 degrees, supinated 10 degrees
Humeroradial: Full extension and supination

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Capsular pattern of elbow joint

Flexion > Extension

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Proximal & Distal Radioulnar Joint articulations and joint type

Prox: 
-ulnar radial notch with head of radius
-capitulum of humerus
-annular ligament
Dist:
-Ulnar notch of radius with head of ulna
-TFCC
Type:
-uniaxial pivot joint

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Pronation occurs as a result of ____ crossing over the ____ at proximal radioulnar joint

radius

ulna

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Rotation occurs at the…

proximal radioulnar joint

Slide of the concave surface of the _____ on the radius around the ulnar head at the distal radioulnar joint in OKC

ulnar notch

Proximal Radioulnar Joint AK

Supination: lateral rotation
Pronation: medial rotation

Proximal Radioulnar Joint Arthrokinematics

Rotation of the head of the radius on the ulnar radial notch within the annular ligament

Distal Radioulnar Joint Osteokinematics

Supination/pronation

Distal Radioulnar Joint Arthrokinematics

Concave ulnar notch of radius on convex head of the ulna
Supination: roll and slide laterally
Pronation: roll and slide medially

What compensatory shoulder motion could help someone who is lacking in forearm pronation and/or supination to increase this forearm ROM? (this is open chain)

Pronation comp pattern: Shoulder IR | Supination comp pattern: Shoulder ER

Closed chain supination & pronation

humerus and ulna rotate relative to a fixed radius/hand starting position: shoulder in IR, forearm is supinated -radius and ulna are parallel in supination -moving into pronation requires ER of the humerus and ulna -moving back to supinated position results in IR of humerus and ulnar relative to radius/hand

Pronation and Supination are a result of ____ and ____ of the GH, respectively in CKC

ER and IR

Motion is a result of the ____ and ____ muscles to move from supination to pronation in CKC

infraspinatus and pronator quadratus

Proximal radio-ulnar joint articulation in WB/CKC, what is moving on what?

Annular ligament & radial notch of ulna rotate around a fixed radial head

Proximal radio-ulnar joint NWB/OKC

Radial head rotates within a ring formed by the annular ligament & the radial notch of the ulna

Distal radio-ulnar joint | WB/CKC

Convex ulnar head rolls and slides in opposite directions on the concave ulnar notch of the radius

Distal radio-ulnar joint | NWB/OKC

Concavity of the ulnar notch of the radius rolls and slides in similar directs on the convex ulna head

Proximal Radioulnar Joint Closed and Open packed positioning

Closed: 5 degree of supination Open: 70 degree of flexion, 35 degree of supination

Capsular pattern of Proximal radioulnar joint

supination=pronation

Distal radioulnar joint closed and open packed positioning

Closed: 5 degree of supination Open: 10 of supination

Torque Generation of the Elbow Flexors: | Flexor Torque is 20-25% greater with the elbow in a ____ position compared to ____ position

supinated pronated Allows increased flexor moment arm of the biceps & brachioradialis when forearm is supinated

Brachialis

"workhorse" of elbow flexors - large muscle volume - active involvement in all types of elbow flexion

Torque generation of the elbow extensors: | Elbow extension typically combined with shoulder flexion in what activities?

explosive pushing activities | -position minimizes rate and amount of shortening required by triceps to extend elbow

Torque generation of the elbow extensors: | Anterior delt

important synergist to counter shoulder extension potential of triceps

What is the position for the strongest isometric coactivation of elbow flexors and extensors? When do we use this position?

- 90 degrees of elbow flexion | - position utilized for activities requiring strong, rigid elbow

Pronation/Supination & Shoulder ER/IR OKC

Functionally - pronation associated with IR - supination associated with ER - combo allows for hand to rotate nearly 360 degrees in space

Important to keep in mind when testing forearm pronation and supination

Arm held pressed to side with elbow at 90 allows to block rotation torque from humerus

Supinator versus Biceps Brachii

Supinator muscle -Generates significant EMG activity with supination at any angle Biceps muscle -Also a primary supinator -Normally recruited with high power supination activities, particularly those in elbow flexion

High-power Supination Torque: | Screwdriver example, what muscles are recruited? Co-contractors?

- Biceps recruited to assist supinator and extensor pollicis longus - Triceps must co-contract to prevent biceps from actually flexing the elbow and shoulder during supination effort

Law of Parsimony

- States that nervous system tends to activate the fewest muscles or muscle fibers possible for the control of a given joint action - Goal of energy efficiency - Activation of large, polyarticular muscles initiated for more dynamic or highly resisted activities

Pronator Teres vs Pronator Quadratus, which is higher power/lower power?

- Lower powered activities utilize pronator quadratus | - Higher powered activities also recruit pronator teres

Synergistic Relationship between Pronator Teres & Triceps

Highest EMG activation noted in pronator teres with higher powered pronation activities Ie Unscrewing overtightened screw with R hand or just prior to release phase of pitching a baseball Triceps acts as synergist to counter tendency of pronator teres to also flex the elbow