Elbow joint

Mnemonic

Here are is a mnemonic that can help you remember the articulations involved in the elbow joint.

CRAzy TULips

• Capitulum = RAdius (capitulum of the humerus articulates with the head of radius)
• Trochlea = ULnar (the trochlea of the humerus articulates with the trochlear notch of the ulna)

Now that you've learned everything about the elbow joint, put that knowledge to the test with the following quiz!

Do you want some help in learning the elbow joint? The following study unit will teach you that topic in a fun and engaging way. 

Flexion

Most of the muscles producing flexion are found in the anterior compartment of the arm. There are two muscles in this compartment that produce flexion at the elbow joint:

• Biceps Brachii originates as two heads. The tendon of the long head originates from the supraglenoid tubercle of the scapula. It passes through the joint capsule of the shoulder joint and through the bicipital groove on the anterior surface of the humerus. The short head of the biceps brachii muscle originates from the coracoid process of the scapula. These heads join together to form the biceps brachii muscle belly. The muscle inserts via a single tendon onto the radial tuberosity distal to the elbow joint. In the forearm, there is a continuation of this tendon as a flattened connective tissue sheath, the bicipital aponeurosis. This aponeurosis blends with the deep fascia in the anterior forearm. 
• Brachialis originates from the distal half of the anterior surface of the humerus, as well as from the intermuscular septa on either side of the anterior compartment. It is located deep to the biceps brachii muscle. It forms a singular tendon that inserts onto the tuberosity of the ulna. 

Both the biceps brachii and brachialis muscles are innervated by the Musculocutaneous nerve.

While the biceps brachii and the brachialis muscles are the main flexors of the elbow joint, the brachioradialis muscle is also involved in flexion of the forearm at this joint. Brachioradialis originates for the lateral aspect of the distal humerus above the lateral epicondyle. It inserts onto the lateral aspect of the distal radius. Although this muscle is primarily in the forearm, it crosses the elbow joint so therefore it acts on the elbow joint. It is innervated by the radial nerve. 

Mnemonic

Learning the muscles that bend the elbow becomes child's play if you anchor them to a mnemonic like the one below.

3 B's bend the elbow

• Biceps
• Brachialis
• Brachioradialis

Extension

Extension of the forearm at the elbow joint is the increase of the angle at the elbow to bring the forearm back to the anatomical position from a flexed position. There is one muscle involved in extension, the triceps brachii muscle. It is the only muscle in the posterior compartment of the arm.

Triceps Brachii originates as three heads. The long head originates from the infraglenoid tubercle of the scapula, the lateral head originates from the lateral aspect of the humerus above the radial groove, and the medial head originates from the medial aspect of the humerus below the level of the radial groove. The three heads converge on a single tendon that inserts onto the olecranon of the ulna. It is supplied by the radial nerve, which passes down through the arm in the radial groove between the lateral and medial heads of the muscle.

While flexion and extension are the only movements that can occur at the elbow joint itself, movement is also afforded at the proximal radioulnar joint, which contributes to the elbow joint. Movements at this joint are called pronation and supination. These are rotational movements that occur when the distal end of the radius moves over the distal end of the ulna by rotating the radius in the pivot joint formed by the circular head of the radius, the radial groove of the ulna and the annular ligament.

Pronation and supination are easily visualised when the elbow is flexed at 90°. Supination is where the palm of the hand is facing upwards; pronation is rotation of the forearm so that the palm is facing downwards. In the anatomical position, the forearm is in the supine position. Pronation in the anatomical position is movement of the forearm so that the palm is facing posteriorly.