The Elbow Joint And Forearm Flexors/extensors

Front 1

Humeroulnar joint

Back 1

* acts in flexion/extension
* stabilized by...
1. the ulnar collateral ligament - attaches the medial epicondyle of the humerus to the medial side of the head of the ulna
2. the lateral (radial) collateral ligament - attaches the lateral epicondyle of the humerus to the lateral side of the head of the ulna
3. the elbow joint capsule
4. the annular ligament - wraps around the head of the radius and "ties" it to the ulna

Front 2

Biceps brachii

Back 2

* acts as a flexor when the hand is supinated
* when pronated, contraction results in strong supination
* 2 branches extend from the supraglenoid tubercle (long head) and the coracoid process (short head) of the scapula, then fuse into a common tendon and insert primarily at the radial tuberosity (and a secondary insertion with the aponeurosis that blends into the periosteum of the ulna)

Front 3

Supinator

Back 3

*supinates the forearm
* extends from the lateral epicondyle of the humerus and from the ulna below the radial notch, wraps around the back of the radius and inserts on the anterior aspect

Front 4

Pronator teres

Back 4

* pronates the forearm
* also acts as a weak flexor
* extends from the anterior surface of the medial epicondyle of the humerus to the lateral side of the radius

Front 5

Pronator quadratus

Back 5

* pronates the forearm
* extends from the distal ulnar shaft to the distal radial shaft

Front 6

Brachialis

Back 6

* flexes the elbow
* extends from the anterior distal half of the humerus shaft to the coronoid process of the ulna

Front 7

Brachioradialis

Back 7

* flexes the elbow
* increases the speed and force of flexion
* extends from the lateral side of the distal humerus to the distal end of the radius (near the styloid process)

Front 8

Humeroradial joint

Back 8

* acts in rotation

Front 9

Superior radioulnar joint

Back 9

* acts during pronation and supination

Front 10

Triceps

Back 10

* primary extensor of the forearm
* 3 heads which unite at a common tendon and insert at the olecranon process of the ulna
1. long head extends from the infraglenoid tubercle - can serve as a support for the shoulder joint when the arm is abducted
2. medial (aka deep) head extends from the posterior aspect of the humerus, inferior to the radial groove
3. lateral head extends from the posterior aspect of the humerus, superior to the radial groove

Front 11

Anconeus

Back 11

* extends the elbow and stabilizes it during pronation and supination
* extends from the lateral epicondyle of the humerus to the olecranon process of the ulna