Yatreyu: Created page with "'''Palmaris Longus''' is a slender, fusiform muscle of the volar forearm running from the medial epicondyle to the palmar aponeurosis. It is anatomically one of the most variable muscles in the body — congenitally absent in 12–20% of people of occidental descent, and subject to numerous positional and attachment variations that carry clinical consequences for median and ulnar nerve entrapment. Its trigger points (TrPs) are distinguished from all other forearm muscles..."

2026-05-27T15:51:56Z

Created page with "'''Palmaris Longus''' is a slender, fusiform muscle of the volar forearm running from the medial epicondyle to the palmar aponeurosis. It is anatomically one of the most variable muscles in the body — congenitally absent in 12–20% of people of occidental descent, and subject to numerous positional and attachment variations that carry clinical consequences for median and ulnar nerve entrapment. Its trigger points (TrPs) are distinguished from all other forearm muscles..."

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'''Palmaris Longus''' is a slender, fusiform muscle of the volar forearm running from the medial epicondyle to the palmar aponeurosis. It is anatomically one of the most variable muscles in the body — congenitally absent in 12–20% of people of occidental descent, and subject to numerous positional and attachment variations that carry clinical consequences for median and ulnar nerve entrapment. Its trigger points (TrPs) are distinguished from all other forearm muscles by their referred '''prickling, needle-like pain''' over the palm rather than the deep-tissue aching quality of most myofascial referrals. This quality difference makes the palmaris longus one of the more straightforward muscles to identify clinically when active.

== Anatomy ==

* '''Proximal attachment:''' Medial epicondyle of the humerus (via common flexor tendon)
* '''Distal attachment:''' Triangular palmar aponeurosis and transverse carpal ligament. At the wrist the tendon passes '''superficial''' to the flexor retinaculum (unlike the finger flexors which pass beneath it). The tendon stands out clearly when the hand is actively flexed and the palm cupped.
* '''Innervation:''' Median nerve, lateral cord; anterior divisions, upper and middle trunks of the brachial plexus; variable spinal levels — most commonly C7 and C8, sometimes C6 and C7, or C7, C8 and T1
* '''Primary function:''' Tensing the palmar fascia (the distinctive anatomical function); flexion of the hand at the wrist; probable weak pronation against resistance; possible weak elbow flexion

'''Variability:''' The muscle belly is normally in the proximal half of the forearm, but may be distally placed, double-bellied, or represented by an anomalous distal belly. Congenital absence: 12.7–20.4% in occidental and Black populations; only 2.2–3.4% in Oriental populations. Bilateral absence is nearly twice as common as unilateral absence. Absence is slightly more common in females and in whites. The belly location determines where TrPs will be found — the examiner must first establish that the muscle exists and where its belly lies before examining for TrPs.

'''Palmar aponeurosis:''' Two layers — a superficial longitudinal layer extending from the palmaris longus tendon to the fingers (fibres fan into bundles over each flexor tendon, some attaching to the skin at the base of the fingers, others continuing into the digital sheaths); and a deep transverse layer blending with the transverse metacarpal and palmar ligaments.

== Referred Pain Pattern ==

The palmaris longus refers a '''distinctive prickling, needle-like sensation''' rather than aching pain. The patient typically describes it as fine needles in the palm. This quality is shared with the platysma among forearm and upper limb muscles.

Pattern:
* '''Central palm''' (essential zone)
* Extends to the base of the thumb and to the distal palmar crease, but '''not into the digits'''
* Spillover to the distal volar forearm

The prickling quality is the critical differentiating feature from other causes of volar wrist and palmar pain.

== Activation and Perpetuating Factors ==

* Excessive use of the grasping function of the hand
* Direct trauma: fall on the outstretched hand
* Forcibly pressing or holding a tool in the cupped palm: screwdrivers, trowels, chisels, carpentry tools
* Holding a tennis racquet with the end of the handle pressed into the palm
* Leaning on a cane with an angular (rather than round) handle pressing into the palm

TrPs in the palmaris longus may develop as '''satellite TrPs''' of key TrPs in the distal medial head of the [[Muscle:Triceps_Brachii]] (TrP5), which refers pain to the medial epicondylar region where the palmaris longus originates.

'''Dupuytren's contracture association:''' Patients with Dupuytren's contracture commonly have active TrPs in the palmaris longus fibres. Whether TrPs and contracture are aetiologically related is unknown, but the referred palmar tenderness from TrPs likely accounts for why patients with Dupuytren's contracture often associate their pain with manual work trauma (even though repeated trauma is increasingly rejected as a primary cause of the contracture itself).

== Clinical Examination ==

=== History and Functional Assessment ===

Key features: pain and tenderness in the '''palm''' described as prickling or needle-like; difficulty using tools because handle pressure in the palm becomes intolerable; tender nodules in the palm that the patient can localise. This is not the lateral epicondylar or dorsal wrist pain of the extensor group — the pain is entirely volar and palmar.

=== Confirming the Muscle Exists ===

Before examining for TrPs, confirm the palmaris longus is present:
* Have the patient '''cup the hand vigorously''' with the wrist in neutral — the tendon stands out clearly at the wrist, superficial to the transverse carpal ligament
* The tendon may disappear when the hand is relaxed; this is normal
* Slowly move the strongly cupped hand from extension to flexion — the tendon prominence depends on wrist position
* If no tendon is visible with vigorous palm cupping, the muscle is likely absent (up to 20% of the population)

The belly location (and thus TrP location) may be high or low in the forearm depending on the individual anatomy.

=== Trigger Point Examination ===

Central TrPs are found in the midbelly region of the muscle — usually the proximal half of the forearm, but variable depending on the individual's anatomy.

* Roll the TrP nodule back and forth between two fingers — a palpable nodule in a taut band is characteristic
* Stimulation by pressure typically elicits the referred prickling pain in the palm (the characteristic pattern)
* LTR: seen as flexion of the hand at the wrist
* An attachment TrP may also be present proximally near the medial epicondyle

'''Important palpation caution:''' If intense spontaneous pain is already present due to maximal TrP hyperactivity, digital compression of the TrP cannot increase the already maximum referred sensation — the examiner may incorrectly assume the tender spot is not responsible for the patient's complaint. This same pitfall occurs in other muscles.

For TrP diagnostic criteria, see [[Concept:Trigger_Point]].

=== Dupuytren's Contracture Palpation ===

In a palm developing Dupuytren's contracture, palpation reveals discretely tender nodules (usually beginning on the ulnar side of the palm, short of the distal palmar crease) against a background of diffuse referred palmar tenderness. The TrP-referred sensation has the characteristic prickling quality; the diffuse soreness does not.

=== Joint Play Assessment ===

Assess joint play in the wrist articulations. Loss of joint play should be identified and corrected alongside TrP treatment.

== Entrapment ==

No nerve entrapments from TrPs in this muscle have been observed. However, '''anatomical variations''' of the palmaris longus are a recognised cause of:

* '''Median nerve entrapment at the wrist''' — when the tendon passes beneath (rather than above) the volar carpal ligament; when an anomalous distal belly compresses the median nerve against the underlying tendons; when a reversed or bifid muscle belly occupies space in the carpal tunnel. These have been confirmed surgically and relieved by decompression.
* '''Ulnar nerve entrapment''' at the ulnar tunnel at the wrist — via accessory palmaris longus variants.

When the palmaris longus anomalously extends under the carpal ligament, TrPs increasing muscle tension and nodular enlargement will aggravate the entrapment symptoms. TrP inactivation should be attempted before assuming entrapment is purely structural.

== Differential Diagnosis ==

{| class="wikitable"
! Condition !! Must be present !! Must be absent !! Merely possible
|-
| '''Palmaris longus TrPs''' || Taut band with nodule in palmaris belly; prickling referred pain to the palm reproduced by TrP compression; LTR = wrist flexion || Deep aching quality of pain (prickling is the hallmark); neurological deficit || Palmar tenderness; volar forearm pain; Dupuytren's nodules
|-
| '''Carpal tunnel syndrome''' || Positive Phalen's test (≥60 sec wrist flexion reproduces symptoms); nocturnal median nerve territory paraesthesiae; Tinel's sign at carpal tunnel || Prickling palmar pain reproduced by palmaris belly TrP compression || Palmar pain; volar wrist tenderness; hand weakness
|-
| '''Flexor carpi radialis TrP''' || Taut band with spot tenderness in FCR belly; referred pain deep, aching in quality to the volar wrist || Prickling quality of pain || Volar wrist pain; pain with resisted wrist flexion
|-
| '''Pronator teres TrP''' || Taut band in proximal volar forearm; aching referred pain along volar forearm; may mimic CTS || Prickling quality of pain || Volar forearm and wrist pain
|-
| '''Brachialis TrP''' || Taut band in brachialis (anterior arm); aching referred pain to the base of the thumb volar surface || Prickling quality || Volar thumb pain; antecubital aching
|-
| '''Dupuytren's contracture''' || Nontender fibrous contracted bands in palmar aponeurosis; finger(s) held in fixed flexion; progressive course || || Palmar nodules; palmar tenderness (TrPs commonly coexist and account for the tenderness)
|}

== Treatment ==

=== Spray and Stretch ===

# Patient seated, forearm of the affected side supported on a padded surface
# Simultaneously '''extend the fingers and the hand at the wrist''' — both must be extended fully for adequate stretch
# Extending the forearm at the elbow does not add to the passive stretch for this muscle
# Vapocoolant applied in a '''distal direction''' over the muscle and palm

Spray-and-stretch may be alternated with TrP pressure release. After the palmaris longus is treated, stretch and spray the entire forearm flexor group (hand and finger flexors) to eliminate any associated parallel-muscle TrP involvement.

'''Residual palmar fascia contracture:''' After TrP inactivation, mild to moderate palmar fascia contractures may be stretched by firmly and regularly extending the fingers and palm under warm water, or while applying 2–3 watts/cm² of ultrasound. The more advanced the fibrotic contracture, the more likely that local tenderness will persist after TrP inactivation.

For general principles see [[Concept:Apropos_Treatment]].

=== Trigger Point Injection ===

Patient supine, affected elbow in extension.

* Locate TrPs by palpation (midbelly, usually proximal half of forearm)
* Probe and inject each TrP with 0.5% procaine
* Immediately after injection: passive stretching with vapocooling → moist heat
* Full active ROM

For palmar nodules that remain tender after TrP inactivation: inject each with approximately 0.3 ml of soluble steroid (e.g. dexamethasone sodium phosphate) diluted to approximately 0.5% solution in procaine. This may halt fibrosis progression but cannot reverse advanced palmar contracture.

For general injection principles see [[Concept:Trigger_Point_Injection]].

== Patient Education ==

* Avoid activities that press or hold tools forcibly in the cupped palm until TrPs are inactive
* Use tools with rounded, padded handles rather than angular handles
* Avoid sustained palm-cupping positions — the novice worker tends to maintain a tightly cupped grip for longer periods than the skilled craftsman
* Inactivate any triceps brachii TrPs (particularly TrP5, distal medial head) — these are the key TrP source that can drive palmaris longus as a satellite
* Self-stretch: extend the fingers and hand at the wrist in a warm bath or shower (Fig. 37.4 position in T&S)

== Satellite Trigger Points ==

Key TrP sources driving palmaris longus as satellite:
* [[Muscle:Triceps_Brachii]] (TrP5, distal medial head) — refers pain to the medial epicondylar region; inactivate this first when palmaris longus TrPs recur

Frequently associated (parallel involvement):
* [[Muscle:Flexor_Digitorum_Superficialis]] and [[Muscle:Flexor_Digitorum_Profundus]] — hand and finger flexors; treat together as a group after palmaris longus release
* [[Muscle:Flexor_Carpi_Radialis]] and [[Muscle:Flexor_Carpi_Ulnaris]] — the palmaris longus lies between these two muscles

== Related Pages ==

* [[Muscle:Triceps_Brachii]] — key TrP source (TrP5) for palmaris longus satellite involvement
* [[Muscle:Flexor_Carpi_Radialis]] — adjacent volar wrist flexor; examine together
* [[Muscle:Flexor_Carpi_Ulnaris]] — adjacent volar wrist flexor; examine together
* [[Concept:Trigger_Point]] — diagnostic criteria, taut band, LTR, contraction knot
* [[Concept:Apropos_Treatment]] — general treatment principles
* [[Concept:Trigger_Point_Injection]] — injection principles and post-injection protocol

== References ==

* Travell JG, Simons DG. ''Myofascial Pain and Dysfunction: The Trigger Point Manual, Volume 1: The Upper Half of Body''. 2nd ed. Baltimore: Williams & Wilkins; 1999. Chapter 37.

[[Category:Muscle]]
[[Category:Vol1 Ch37]]
[[Category:Forearm and Hand]]

Muscle:Palmaris Longus - Revision history