Elbow and Forearm

Humeroulnar joint

trochlea of humeurs → trochlear notch ulna

Humeroradial joint

capitulum of humerus → fovea at head of radius

What kind of joint is is the elbow joint?

modified (rotating) hinge joint

How many degrees of freedom does the elbow joint have?

1 (flexion and extension)

Where is the axis of the elbow joint?

centers of capitulum and trochlea of humerus

at a slight diagonal

Carrying angle

formed by the longitudinal axis between humerus and ulna when the elbow is in extension and the forearm is supination

Cubitus valgus

ulna is angled 5-15 degree lateral in relation to humerus

What is the functional signficance of carrying angle?

forearms clear hips during ambulation and when carrying items (doesn’t keep constantly hitting the hips

Excessive cubitus valgus

>15 degrees lateral deviation of forearm

Cubitus varus

<5-15 degrees of valgus medial deviation of forearm

Bony configuration of elbow joint

tight fit of humeroulnar articulation

Elbow Extension: Bony configuration

olecranon process of ulna fits into olecranon fossa of humerus

Elbow Flexion: Bony configuration

coronoid process of ulna fits into coronoid fossa of humerus

What does the joint capsule enclose?

humeroulnar joint

humeroradial joint

proximal radiounlar joint

The joint capsule is lined with

synovial membrane

What are the ligaments supporting the elbow joint

lateral (radial) collateral ligament and annular ligament

medial (ulnar) collateral ligament

Lateral (radial) collateral ligament and annular ligament resist _____ directed forces?

varus/medially

Medial (ulnar) collateral ligament resist ___ directed forces?

valgus/laterally

What bones are in the forearm?

radius and ulna (parallel to one another)

What are the 2 pivot joints in the forearm?

proximal radioulnar joint

distal radioulnar joint

Proximal radioulnar joint

head of radius → radial notch of ulna

Distal radioulnar joint

head of ulna → ulnar notch of radius

Where is the forearm’s axis of motion?

through the head of the radius proximally and the head of the ulna distally

How many degrees of freedom does the forearm have?

1 (supination and pronation)

The proximal radioulnar joint is stabilized by

annular ligament

lateral/radial collateral ligament

oblique cord

quadrate ligament

Annular Ligament

fits around radial head

attaches to the ulna on either side of radial notch

Oblique Cord/Quadrate ligament

stability of forearm

Distal radioulnar joint is stabilized by

triangular fibrocartilage complex

anterior (palmer/volar) radioulnar ligaments

posterior (dorsal) radioulnar ligament

Interosseous Membrane

fibrous sheet that binds radius to ulna

provides stability by reinforcing PRUJ and DRUJ

provides stable attachment for several extrinsic muscles of the hand

aborbs shock

distributes and transmits forces proximally through upper limb

Weightbearing on upper extremities and holding object when object is superior

compressive forces directed proximally along forearm and elbow

Holding object when object is inferior

distraction forces directed distally along forearm and elbow

Muscles that flex the elbow are positioned ____ to the elbow joint axis

anterior

Maximum torque for active elbow flexion is at?

90 degrees flexion and forearm supination (greatest internal force moment arm)

What are the elbow flexor muscles

Biceps brachii

Brachialis (main mover)

Brachioradialis

Pronator teres (assists)

Muscles that extend the elbow are positioned ___ to the elbow joint axis

posterior

What are the elbow extensors?

triceps brachii (main one)

anconeus (assists)

What muscle produced the majority of elbow extensor torque?

triceps brachii

Muscles that supinate the forearm are positioned ____ to the forearm axis joint

lateral

What are the forearm supinators?

biceps brachii (high powered supination tasks)

supinator (smaller muscle)

Muscles that pronate the forearm are positions ___ to forearm joint axis

medial

What are the forearm pronator muscles?

Pronator teres (stronger pronator)

Pronator Quadratus (small)