Palmaris longus
Musculus palmaris longus
Also known as: palmaris
A small, variable superficial flexor with a long, thin tendon to the palmar aponeurosis. It is absent in about 14% of people and is a popular tendon graft.
Overview
Palmaris longus has a short belly arising from the medial epicondyle and a long, slender tendon that passes superficial to the flexor retinaculum into the palmar aponeurosis. The tendon becomes prominent when the thumb and little finger are pinched together with the wrist flexed. The median nerve lies just deep and slightly lateral to it at the wrist. Palmaris longus is a weak wrist flexor and tenses the palmar aponeurosis. It is absent on one or both sides in ≈14% of people (prevalence varies widely between populations), with no functional loss. That makes its tendon ideal for grafts and reconstructions, such as ulnar collateral ligament ("Tommy John") repair.
Anatomy
- Origin
Medial epicondyle of the humerus (common flexor origin).
- Insertion
Distal half of the flexor retinaculum and the apex of the palmar aponeurosis.
- Action
Flexion of the wrist; tensing of the palmar aponeurosis.
- Innervation
Median nerve.
- Nerve roots
C7–C8
- Arterial supply
Ulnar artery (anterior ulnar recurrent) and radial artery branches.
- Relations
Superficial to the flexor retinaculum. The median nerve lies deep to it at the wrist. The palmar cutaneous branch of the median nerve runs beside it.
Function
- Weakly flexes the wrist
- Tenses the palmar aponeurosis
Clinical significance
Tendon graft
It is the most commonly harvested tendon graft in hand and elbow surgery, after its presence has been confirmed with the Schaeffer test (opposing thumb and little finger with the wrist flexed).
Compiled from standard anatomy and physiology references — see the Muscular System sources. For education only; not medical advice.