Palmaris Longus Muscle Beneath the Skin, Lateral View

Description

Running along the superficial anterior compartment of the forearm, the palmaris longus lies between flexor carpi radialis laterally and flexor carpi ulnaris medially, its slender muscle belly giving way distally to a long tendon that crosses superficial to the flexor retinaculum toward the palmar aponeurosis. From a lateral perspective you also pick up key neighbors that frame it, including brachioradialis on the radial (lateral) border and pronator teres crossing obliquely from the medial epicondyle toward the proximal radius. Radius and ulna sit deep to the flexor mass, with the carpal bones and metacarpals forming the distal scaffold at the wrist and palm. Small muscle, long tendon. Clinically, palmaris longus matters out of proportion to its size because its tendon is frequently harvested for grafting (for example, ulnar collateral ligament reconstruction of the thumb, ptosis repair, and various tendon reconstructions) and its absence or duplication changes surface anatomy and operative planning. The lateral view supports teaching of the classic palmaris longus “wrist flexion with thumb to little finger” test by clarifying where the tendon should stand out in the volar forearm relative to the radial-sided flexors and the flexor retinaculum, and it also helps distinguish a prominent tendon from pathology such as a palmaris longus variant that can contribute to median nerve irritation proximal to the carpal tunnel. Use this illustration in upper limb gross anatomy modules, rehabilitation and palpation labs, and surgical education content covering volar forearm approaches, tendon graft selection, and patient-facing explanations of why a tendon may be taken from the forearm without meaningful loss of function. It also fits well in anatomy atlases and orthopedic or plastic surgery texts that need a clear relationship between superficial flexor fascia, tendon course, and underlying radius and ulna. Anatomical accuracy verified by SciePro's Medical Advisory Board.