Posterior compartments of forearm

Posterior Compartments of Forearm

The forearm is divided into anterior and posterior compartments, each containing various muscles, nerves, and blood vessels. In this article, we will focus on the posterior compartments of the forearm. These compartments are located on the backside of the forearm and play a crucial role in the movement and functionality of the hand and wrist.

Muscles

The posterior compartments of the forearm consist of several muscles that are responsible for various movements of the hand and wrist. These muscles can be categorized into two groups: superficial and deep muscles.

Superficial Muscles

The superficial muscles of the posterior compartment include the extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris. These muscles are primarily involved in extending the wrist, fingers, and thumb.

• Extensor carpi radialis longus: This muscle originates from the lateral supracondylar ridge of the humerus and inserts into the base of the second metacarpal bone. It extends and abducts the wrist.

• Extensor carpi radialis brevis: Originating from the lateral epicondyle of the humerus, this muscle inserts into the base of the third metacarpal bone. It also extends and abducts the wrist.

• Extensor digitorum: This muscle originates from the lateral epicondyle of the humerus and extends along the forearm, inserting into the base of the distal phalanges of the fingers. It extends the fingers and assists in wrist extension.

• Extensor digiti minimi: Originating from the common extensor tendon, this muscle inserts into the base of the proximal phalanx of the little finger. It extends the little finger and assists in wrist extension.

• Extensor carpi ulnaris: This muscle originates from the lateral epicondyle of the humerus and inserts into the base of the fifth metacarpal bone. It extends and adducts the wrist.

Deep Muscles

The deep muscles of the posterior compartment include the supinator, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis. These muscles are responsible for more specialized movements of the hand and wrist.

• Supinator: Originating from the lateral epicondyle of the humerus and the proximal ulna, this muscle wraps around the radius bone. It supinates the forearm, allowing the palm to face upward.

• Abductor pollicis longus: This muscle originates from the posterior surface of the ulna and the interosseous membrane. It inserts into the base of the first metacarpal bone and abducts the thumb.

• Extensor pollicis brevis: Originating from the posterior surface of the radius and the interosseous membrane, this muscle inserts into the base of the proximal phalanx of the thumb. It extends the thumb at the carpometacarpal joint.

• Extensor pollicis longus: This muscle originates from the posterior surface of the ulna and the interosseous membrane. It inserts into the base of the distal phalanx of the thumb. It extends the thumb at the interphalangeal joint.

• Extensor indicis: Originating from the posterior surface of the ulna and the interosseous membrane, this muscle inserts into the extensor expansion of the index finger. It extends the index finger.

Nerves and Blood Vessels

The posterior compartments of the forearm are innervated by the radial nerve, which provides motor and sensory functions to the muscles and skin of the area. The radial artery, a major blood vessel, also runs through the posterior compartment, supplying oxygenated blood to the muscles and surrounding tissues.

Clinical Significance

Injuries or conditions affecting the posterior compartments of the forearm can result in functional limitations and pain. Common conditions include tendinitis, strains, and nerve entrapment syndromes such as radial tunnel syndrome. Proper diagnosis and treatment are essential for restoring normal function and relieving symptoms.

See Also

• Forearm
• Anterior Compartments of Forearm
• Radial Nerve
• Radial Artery