Forearm Anatomy Overview

Antebrachium Overview

• The antebrachium refers to the forearm, running from the elbow to the wrist.
• Composed of two bones: ulna (medial aspect) and radius, connected by the interosseus membrane.

Interosseus Membrane

• Tough connective tissue that stabilizes the ulna and radius, allowing mobility.

Pronation and Supination

• Loose arrangement of the ulna and radius enables rotation of the forearm, termed pronation and supination.
• The wrist itself does not allow for rotation.

Muscle Compartments of the Antebrachium

• Divided into anterior (flexors) and posterior (extensors) compartments, with proximal muscle bellies and distal tendons.
• Proximal attachment is typically higher up (nearer to the elbow), which can contribute to injuries like tendinitis.

Anatomy of the Ulna

• Medial bone of the forearm, featuring a broad proximal end and narrowing distally.

Anterior Compartment Muscles

• Anterior compartment consists of superficial, intermediate, and deep muscle layers.
• Superficial muscles include Flexor Carpi Ulnaris, Palmaris Longus, Flexor Carpi Radialis, and Pronator Teres.
• Originates primarily from the common flexor tendon at the medial epicondyle.

Flexor Carpi Ulnaris

• Most medial of the anterior superficial muscles, innervated by the ulnar nerve.
• Originates from the medial epicondyle and olecranon process, attaching distal to the pisiform bone and fifth metacarpal.
• Function: allows wrist flexion and ulnar deviation.

Palmaris Longus

• Lateral to Flexor Carpi Ulnaris, often absent in 14% of the population.
• Originates from the medial epicondyle; attaches to the flexor retinaculum and palmar aponeurosis.
• Innervated by the median nerve; aids in tensing the palmar aponeurosis.

Flexor Carpi Radialis

• Innervated by the median nerve; responsible for wrist flexion and radial deviation.
• Originates from the medial epicondyle; attaches to the base of the second metacarpal.

Intermediate and Deep Muscles

• Intermediate layer: Flexor Digitorum Superficialis, which divides into four tendons reaching distal phalanges.
• Deep muscles include Flexor Digitorum Profundus (runs to distal phalanges 2-5), Flexor Pollicis Longus (flexes thumb), and Pronator Quadratus (primary pronator).

Posterior Compartment Muscles

• Divided into superficial, deep, and outcropping muscles.
• Mainly involved in wrist and digit extension, and innervated by the radial nerve.

Brachioradialis

• Unique muscle that flexes the elbow, originating from the supinator ridge, and attaches to the radius.
• Supplied by the radial recurrent artery.

Extensor Muscles Overview

• Superficial muscles include Extensor Carpi Radialis Longus/Brevis, Extensor Digitorum, Extensor Digiti Minimi, and Extensor Carpi Ulnaris.
• Common origin is the lateral epicondyle of the humerus, with functions primarily focused on wrist extension and radial/ulnar deviation.

Clinical Conditions

• Golfer's elbow refers to medial epicondylitis, while Tennis elbow refers to lateral epicondylitis.

Blood Supply and Innervation

• Anterior compartment is supplied by ulnar and radial arteries and innervated mainly by the median and ulnar nerves.
• Posterior compartment is supplied by the posterior interosseous artery.