Palmaris Longus Muscle Beneath the Skin, Medial View

Description

Arising from the medial epicondyle of the humerus, the palmaris longus runs superficially along the anterior forearm, its fusiform belly tapering distally into a slender tendon that becomes prominent just proximal to the wrist. Medially it lies close to flexor carpi ulnaris, while flexor carpi radialis sits more laterally, and the tendon courses superficial to the flexor retinaculum on its way into the palmar aponeurosis. A semi-transparent integument layer keeps the muscle in situ beneath the skin, with the ulna forming the medial bony border of the forearm and the carpal and metacarpal skeleton providing distal landmarks. Palmaris longus matters because it is both variable and clinically useful: absence is common, and when present the tendon is frequently harvested for grafting in procedures such as tendon reconstruction of the hand or ligament augmentation. At the wrist, its relationship to the median nerve and flexor retinaculum is a practical teaching point, since a superficially placed tendon can be mistaken for other structures during exposure and injection, and an anomalous palmaris longus can contribute to median nerve symptoms. Surface anatomy is the takeaway. This view clarifies why resisted wrist flexion with thumb to little finger opposition makes the tendon stand out in many patients. Use this illustration in gross anatomy lab manuals and surface anatomy modules to orient learners to the medial (ulnar) side of the forearm and the palmar aponeurosis connection. It also fits hand surgery teaching files when discussing tendon graft options, anatomic variants, and safe planes of dissection at the volar wrist. Anatomical accuracy verified by SciePro's Medical Advisory Board.