Palmaris Longus

Origin, Insertion, Action, Innervation

Origin: Medial epicondyle of the humerus (common flexor origin)
Insertion: Flexor retinaculum (transverse carpal ligament) and palmar aponeurosis
Action:
Primary: Tenses the palmar aponeurosis (cups the palm)
Weak wrist flexion
Innervation: Median nerve (C7–C8)

Palpation Guide

Client position: Seated or supine with the forearm supinated and wrist in neutral.
Landmark sequence:

Ask the client to oppose the thumb to the little finger and gently flex the wrist. The palmaris longus tendon becomes the most prominent and superficial tendon at the anterior wrist crease — it is the midline tendon.
The FCR tendon lies just radial (lateral) to palmaris longus. If only one tendon is visible, it is more likely FCR — palmaris longus is absent in ~14% of the population unilaterally and ~8% bilaterally.
The muscle belly is a thin, fusiform shape in the proximal-medial forearm, transitioning to its long tendon approximately one-third of the way down the forearm.
The tendon fans into the palmar aponeurosis distal to the wrist crease — this fascial sheet covers the palm and anchors to the palmar skin.

Tissue feel: The tendon is the most superficial and prominent cord at the anterior wrist. The muscle belly is thin and difficult to distinguish from the surrounding superficial flexors. The palmar aponeurosis feels like a firm sheet of fascia in the central palm.
Confirmation test: Thumb-to-little-finger opposition with gentle wrist flexion makes the tendon pop up. If the tendon is absent, the muscle is absent — this is the Schaeffer test for palmaris longus absence.
Common errors:
Confusing palmaris longus with FCR — FCR is just lateral to palmaris longus and is always present. If only one prominent tendon is visible, confirm which it is by adding radial deviation (FCR tendon becomes more prominent) versus cupping the palm (palmaris longus becomes more prominent).
Assuming palmaris longus absence is pathological — absence is a normal anatomical variant with no functional deficit. The hand functions normally without it.

Trigger Point Referral

Common TrP locations: The TrP is in the small proximal muscle belly, approximately 3–4 cm distal to the medial epicondyle in the superficial anterior forearm.
Referral pattern: Refers to the central palm with a prickling or needle-like quality — often described as a "pins and needles" sensation in the palm.
Clinical significance: The prickling palmar referral is unusual and can be mistaken for median nerve compression or peripheral neuropathy. If a client describes sharp, prickling palm discomfort that does not follow a nerve distribution, check palmaris longus TrPs.

Trigger point referral diagram — coming soon

Image coming soon. For visual reference, see [Palmaris Longus at TriggerPoints.net](http://www.triggerpoints.net/muscle/palmaris-longus).

Clinical Notes

Anatomical significance:

Palmaris longus is the most commonly absent muscle in the body. Its absence has no measurable effect on grip strength or wrist function, confirming its vestigial status. Surgeons frequently use the palmaris longus tendon as a donor for tendon grafts (e.g., reconstructing the UCL of the thumb or flexor tendons) because it can be harvested without functional loss.

Common conditions:

Dupuytren's contracture — palmaris longus inserts into the palmar aponeurosis, which is the tissue affected in Dupuytren's. Progressive thickening and contracture of the palmar aponeurosis pulls the fingers (typically ring and little) into flexion. Palmaris longus hypertonicity does not cause Dupuytren's (which is a fibroproliferative disorder), but the anatomical connection means the tendon and aponeurosis must be assessed together.
Part of the common flexor origin — contributes to conditions/medial-epicondylitis through its medial epicondyle attachment, though its contribution is minor given its small size.
The palmaris longus tendon is the key surface landmark for the median nerve at the wrist — the median nerve lies immediately deep (posterior) and slightly radial to the palmaris longus tendon. This relationship defines where the median nerve enters the carpal tunnel.

What you'll typically find:

Palmaris longus is rarely the primary complaint muscle. When the forearm flexor group is hypertonic, palmaris longus is involved but its contribution is minor relative to FCR, FDS, and FDP.
Its clinical value is as a landmark, not a treatment target. When you find the palmaris longus tendon, you have found the median nerve.

Treatment effects:

The muscle is thin and responds quickly to brief stripping or compression. It rarely requires extensive treatment.
The palmar aponeurosis insertion is more clinically relevant — in clients with palmar fascial tightness, gentle myofascial release of the palmar aponeurosis can improve finger extension ROM and reduce palmar stiffness.

Cautions:

The median nerve lies immediately deep to the palmaris longus tendon at the wrist. Direct compression of the tendon at the wrist crease can compress the median nerve against the transverse carpal ligament. Avoid sustained pressure directly on the palmaris longus tendon at the wrist.

Clinical pearl:

The palmaris longus tendon is the navigation anchor at the anterior wrist — learn to find it instantly. The median nerve is deep to it, the FCR tendon is lateral to it (with the radial artery lateral to FCR), and the FCU tendon is medial to it (with the ulnar nerve and artery medial to FCU). From one tendon, you can locate every clinically important structure at the wrist.

Assessment

Manual muscle testing:

Palmar aponeurosis tension: Ask the client to cup the palm (oppose thumb to little finger) and flex the wrist gently. The palmaris longus tendon is visible if the muscle is present. No formal strength grading is typically performed because the muscle is functionally insignificant.

Stretch test:

Wrist extension with finger extension: Client seated with elbow extended. Passively extend the wrist and spread the fingers. This stretches the palmar aponeurosis and the palmaris longus. Tightness in the central palm suggests palmar fascial restriction.

Related special orthopedic tests:

Schaeffer test — thumb-little finger opposition with wrist flexion to check for palmaris longus presence/absence
Tabletop test — inability to flatten the palm on a table surface suggests Dupuytren's contracture of the palmar aponeurosis

Muscle Groups

Common flexor origin (anatomical �� medial epicondyle):

anatomy/muscles/pronator-teres
anatomy/muscles/flexor-carpi-radialis
Palmaris longus (this article)
anatomy/muscles/flexor-carpi-ulnaris
anatomy/muscles/flexor-digitorum-superficialis (humeral head)

Wrist flexors (functional — weak role):

Median nerve group — forearm (innervation):

anatomy/muscles/pronator-teres
anatomy/muscles/flexor-carpi-radialis
Palmaris longus (this article)
anatomy/muscles/flexor-digitorum-superficialis

Related Muscles

Synergists for wrist flexion (minor role):

anatomy/muscles/flexor-carpi-radialis — primary flexor with radial deviation
anatomy/muscles/flexor-carpi-ulnaris — primary flexor with ulnar deviation

Antagonists:

anatomy/muscles/extensor-carpi-radialis-longus — wrist extension with radial deviation
anatomy/muscles/extensor-carpi-ulnaris �� wrist extension with ulnar deviation

Same origin (common flexor group):

anatomy/muscles/pronator-teres — pronator and weak elbow flexor
anatomy/muscles/flexor-carpi-radialis — wrist flexor and radial deviator

Key Takeaways

Palmaris longus is absent in ~14% of the population with no functional deficit — check for its presence before using it as a landmark.
Its primary clinical value is as a surface landmark: the median nerve lies immediately deep to the palmaris longus tendon at the wrist.
The insertion into the palmar aponeurosis connects it to Dupuytren's contracture — assess the palmar fascia in any client with progressive finger flexion contracture.