Elbow Anatomy

The parts that make up the anatomy of the elbow are important for linking the shoulder, arm and wrist joints. This helps the human being to perform different biomechanical movements thanks to the action of the muscles, ligaments, bones and joints of the elbow.

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Parts and anatomy of the elbow

Bones and joints

• Humerus: The upper part is connected to the scapula through the glenohumeral joint. It is an elongated bone that can be divided into several areas, with the supracondylar crest, coronoid fossa, epicondyle, radial fossa, condyle and trochlea being the areas related to the elbow. The protruding and visible bone that we all call the elbow is the epicondyle.
• Radius: This bone is located on the outside of the forearm and runs parallel to the ulna, it is also elongated and somewhat curved. It connects through its head to the epicondyle of the humerus to form the elbow.
• Ulna: The head of this bone or olecranon connects with the epitrochlea, trochlea and olecranial cavity of the humerus. At the other end of this elongated tissue is the wrist.
• Humerocubital: Connects the ulna via the olecranon and trichoid process to the trochlea of the humerus and its olecranial and coronoid fossae. This enables extension and flexion of the elbow.
• Humeroradial: This joint connects the condyle of the humerus to the head of the radius so that the elbow can perform flexion and extension movements.
• Proximal radioulnar: This is a trochlear type joint and connects the radial notch of the ulnar bone to the radial head of the radius through its joint circumference.

Muscles

• Biceps brachii: It arises from the coracoid process of the scapula and inserts into the tuberosity of the radius bone. The action of this muscle causes flexion, abduction, rotation and articulation of the shoulder as a whole.
• Triceps brachii: Located on the back of the arm from the tuberosity of the scapula and from the top of the humerus to the olecranon. Its main functions include adduction and extension of the forearm.
• Brachialis: This muscle arises from the middle of the humerus and inserts on the coronoid process and tuberosity of the ulna. Its function is to flex the elbow.
• Supinator longus: Also known as brachioradialis. The flexion of the elbow is produced by the action of this muscle, which is located in the humerus (in the supracondylar part) and is inserted in the lateral end of the radius bone.
• Supinator brevis: The work performed by this tissue is to rotate the radius to provoke elbow movements. It originates in the ulna and in the lower area of the humerus, in the lateral epicondyle.
• Pronator teres: This muscle originates from the medial epicondyle, the supracondylar crest and the coronoid process of the ulna. Its action is related to elbow flexion and pronation of the forearm.
• Pronator quadratus: It arises from the ulna and inserts on the radius, precisely in the distal quarter. The work performed by this tissue is pronation of the forearm.
• Anconee: The extension of the forearm is carried out by the action of this muscle, which is born in the lateral epicondyle of the humerus bone and inserts in the superior process of the ulna.
• Posterior ulnar: It is related to the extinction of the ulna at the wrist. It arises from the epicondyle of the ulna and ends at the fifth metacarpal of the little finger.
• Finger extensors: Some of these muscles arise from the elbow area and their job is to extend and contract the phalanges and metacarpals of the fingers.

Ligaments

• Annular ligament: It is located at the top of the radius below the epicondyle and condyle of the humerus. Its task is to strengthen the joint so that the head of the radial bone remains within the greater sigmoid cavity.
• Square: The ligament runs from the radial head to the trochlear notch of the ulna. This allows supination and pronation movements of the joint.
• Posterior: This is a thin ligament that works for the stability of the elbow. It has transverse and vertical fibres, which are used to restrict joint movements.
• Anterior: It is possible to distinguish in this ligament three types of fibres that help cover the cuff of the humerus to limit the movements of the elbow.
• External lateral: This is a less resistant tissue than the fibres of the internal lateral. Its action is to help the annular ligament to help elbow movements occur.
• Internal lateral: It is possible to divide this ligament into posterior, medial and anterior. This is due to its anatomical arrangement within the elbow to reinforce the epitrochlear area and stabilise movements.

Biomechanics of the elbow

• Flexion: This consists of extending the arm to 90° and directing the hand backwards until it touches the ear. The maximum amplitude of this movement is 170° and works the biceps brachii, brachioradialis and brachialis muscles.
• Extension: This is the reverse of flexion. It involves bringing the hand next to the head up to shoulder height at an angle of 90°, taking the trunk as the axis. The triceps brachii, anconeus and brachialis are the muscular structures that act in this biomechanical movement.
• Supination: This action consists of turning the palm of the hand upwards. The muscles responsible for this movement are the biceps brachii and the supinator brevis. The angle of rotation can be between 75 and 90°.
• Pronation: This is the opposite movement to supination. It involves placing the palm of the hand in the direction of the ground and can have an amplitude of between 75 and 90°. The muscles related to this movement are pronator quadratus and pronator teres.
• Neutral: This is an intermediate movement between pronation and supination. That is, the hand is placed with the palm facing inwards towards the body, with the thumb facing upwards.