Muscles of the Lower Arm Under the Skin, Posterior View

Description

Layered beneath the skin, the posterior compartment of the male antebrachium is organized around the superficial extensors arising from the lateral epicondyle and the deeper outcropping muscles that cross the dorsum of the wrist. Laterally, brachioradialis forms the prominent border of the forearm and leads the eye distally toward the radial styloid, while extensor carpi radialis longus and brevis lie just posterior to it. More medially, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris run in parallel toward the dorsum of the hand, their tendons narrowing as they approach the extensor retinaculum; deeper slips such as abductor pollicis longus, extensor pollicis brevis and longus, extensor indicis, and the supinator occupy the proximal and radial side. Tendons dominate the distal field. Posterior and slightly lateral perspectives like this matter because they map tendon paths to palpable landmarks at the wrist and dorsum of the hand, where crowding under the extensor retinaculum creates predictable sites of pain and entrapment. De Quervain tenosynovitis localizes to the first dorsal compartment (abductor pollicis longus and extensor pollicis brevis), while intersection syndrome occurs where those tendons cross the extensor carpi radialis longus and brevis proximally. Proximally, the relationship of the supinator to the deep branch of the radial nerve (posterior interosseous nerve) frames the anatomy behind radial tunnel and posterior interosseous nerve compression. Use this plate for teaching the extensor compartments in gross anatomy and kinesiology courses, for illustrating lateral epicondylitis and dorsal wrist tendinopathies in sports medicine texts, or for preoperative orientation in hand surgery discussions of dorsal approaches and tendon transfers. Anatomical accuracy verified by SciePro's Medical Advisory Board.