Palmaris Longus Muscle

Origin

The palmaris longus muscle originates from the:

- medial epicondyle of humerus, via the common flexor tendon;

- adjacent antebrachial fascia.

The common flexor tendon is the combined tendon for all five superficial muscles in the anterior compartment of the forearm, which are the:

- pronator teres muscle;

- flexor carpi radialis muscle;

- palmaris longus muscle;

- flexor carpi ulnaris muscle;

- flexor digitorum superficialis muscle.

Insertion

The fibers of the palmaris longus muscle travel inferiorly to the hand and insert, via a long tendon, onto the:

- palmar aponeurosis;

- flexor retinaculum of hand.

Key Features & Anatomical Relations

The palmaris longus muscle is one of the muscles of the superficial part of anterior compartment of the forearm. It is a thin, fusiform type of skeletal muscle. In the middle of the forearm, the muscle belly gives rise to a long tendon, which travels inferomedially. At the wrist, the tendon travels superficial to the flexor retinaculum of hand.

The palmaris muscle is located:

- anterior (superficial) to the flexor digitorum superficialis muscle (at its muscle belly) and the median nerve (at its distal tendon);

- medial to the flexor carpi radialis longus muscle;

- lateral to the flexor carpi ulnaris muscle.

Actions & Testing

The palmaris longus muscle is involved in multiple actions:

- flexes the hand at the radiocarpal (wrist) joint;

- stabilizes the palmar aponeurosis and surrounding skin during shearing forces.

The palmaris longus muscle can be tested by flexing the hand at the radiocarpal joint against resistance, during which its tendon can be seen and palpated (Standring, 2016).

List of Clinical Correlates

- The palmaris longus muscle is absent in some individuals

- It is used for some tendon transplant procedures

References

Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41st edn.: Elsevier Limited.