Normal Anatomy of the Elbow
The elbow is a complex joint that allows for the bending (flexion) and straightening (extension) of the arm, as well as rotation of the forearm. It consists of three main bones: the humerus, radius, and ulna, along with various ligaments, muscles, and tendons that work together to enable a wide range of movements. Here’s a comprehensive and simplified breakdown of the normal anatomy of the elbow:
- Humerus: The upper arm bone that articulates with the radius and ulna. Its rounded lower end forms the “capitulum” on the outer side and the “trochlea” on the inner side of the elbow joint.
- Radius: One of the two bones of the forearm. The head of the radius articulates with the capitulum of the humerus, allowing the forearm to rotate.
- Ulna: The other bone of the forearm. Its “olecranon process” forms the bony prominence at the back of the elbow and fits into the olecranon fossa of the humerus during extension.
- Humeroulnar Joint: This hinge joint allows flexion and extension of the elbow. The trochlea of the humerus articulates with the trochlear notch of the ulna.
- Humeroradial Joint: The articulation between the capitulum of the humerus and the head of the radius allows for rotation of the forearm.
- Proximal Radioulnar Joint: The head of the radius pivots within the radial notch of the ulna, enabling rotation of the forearm.
- Medial Collateral Ligament (MCL): Stabilizes the inner side of the elbow joint.
- Lateral Collateral Ligament (LCL): Stabilizes the outer side of the elbow joint.
- Annular Ligament: Encircles the head of the radius, holding it in place against the ulna.
Muscles and Tendons
- Biceps Brachii: Flexes the elbow and supinates the forearm.
- Triceps Brachii: Extends the elbow.
- Brachialis: A primary flexor of the elbow.
- Brachioradialis: Helps flex and stabilize the elbow.
- Pronator Teres and Supinator: Muscles that control forearm rotation.
Nerves and Blood Vessels
- Median Nerve: Provides sensation to the palm and controls certain forearm muscles.
- Ulnar Nerve: Supplies sensation to the ring and pinky fingers and controls hand muscles.
- Radial Nerve: Supplies sensation to the back of the hand and controls muscles that extend the wrist and fingers.
- Brachial Artery: Supplies blood to the elbow and forearm.
Cartilage and Synovium
The elbow joint is lined with articular cartilage, which provides a smooth surface for joint movement. The synovial membrane produces synovial fluid to lubricate the joint and reduce friction.