Palmaris Longus Muscle, Anterior View

Description

Positioned on the anterior (palmar) aspect of the distal forearm, the palmaris longus muscle belly tapers into a long, slender tendon that travels superficially toward the wrist in the midline, just medial to the flexor carpi radialis and lateral to the flexor carpi ulnaris. Distally, the tendon crosses superficial to the flexor retinaculum and expands into the palmar aponeurosis, fanning over the central palm. The course is subcutaneous. In a male adult specimen, this relationship helps separate the palmaris longus tendon from deeper flexor tendons headed through the carpal tunnel. Clinically, palmaris longus matters because its tendon is one of the common donor grafts for reconstructive procedures, including tendon grafting in the hand and forearm and ligament reconstruction such as ulnar collateral ligament (Tommy John) surgery. Its variability is the teaching point, the muscle is absent unilaterally or bilaterally in a substantial minority of individuals, so preoperative identification with the classic wrist flexion and thumb to little finger opposition maneuver prevents an unpleasant surprise in the operating room. Surface anatomy also intersects with median nerve territory, the tendon sits superficial and central while the median nerve and flexor tendons lie deep to the flexor retinaculum, a distinction that guides safe dissection and injection planning at the volar wrist. Educators can drop this anterior forearm and palm view directly into gross anatomy labs, kinesiology modules on wrist flexion and palmar tensioning, or surgical teaching files covering volar approaches and graft harvest technique. Publishers will find it well suited for chapters on forearm flexors, palmar fascia, and clinically oriented surface anatomy of the wrist crease. Anatomical accuracy verified by SciePro's Medical Advisory Board.