Section 01 of 20
Introduction
The lumbricals are four slender muscles in the palm, named for their worm-like shape. Unlike most muscles, they do not attach to bone at their origin. They arise from the tendons of flexor digitorum profundus and travel to the back of the fingers.
Because they link the deep flexor tendons of the palm to the extensor tendons on the back of the fingers, they can flex the metacarpophalangeal (knuckle) joints and extend the interphalangeal joints at the same time, a movement used in writing, typing, and holding a pen or cup.
Section 02 of 20
Origin
| Origin | Tendons of flexor digitorum profundus in the palm. The first and second lumbricals arise from the radial (thumb) side of the tendons to the index and middle fingers; the third arises from the adjacent sides of the middle and ring finger tendons; the fourth arises from the adjacent sides of the ring and little finger tendons. |
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An anatomical image for this section will be added when verified source media becomes available.
Section 03 of 20
Insertion
| Insertion | The radial side of the extensor expansion (dorsal digital expansion) of the index, middle, ring, and little fingers. |
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An anatomical image for this section will be added when verified source media becomes available.
Section 04 of 20
Actions
No dedicated action video is currently available. This movement is explained below and video will be added when verified source media becomes available.
| Primary action | Flexion of the metacarpophalangeal joints with extension of the interphalangeal joints. |
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| Secondary actions | Fine control of finger position. |
| Movement at the joint | Metacarpophalangeal and interphalangeal joints of the fingers. |
| Heads / fiber groups | Four separate small muscles (lumbricals 1–4). |
| Functional examples | Writing and typing; holding a pen; playing instruments; holding a cup with the fingers extended. |
Flexion of the metacarpophalangeal joints
Bends the knuckle joints of the four fingers.
Extension of the interphalangeal joints
Straightens the proximal and distal interphalangeal joints through the extensor expansion.
Coordinated finger position
Produces the pen-holding or table-top position (knuckles bent, fingers straight) and fine control of finger movement.
Section 05 of 20
Nerve Innervation
| Nerve | First and second lumbricals: median nerve (recurrent branch of the digital nerves), roots C8–T1. Third and fourth lumbricals: deep branch of the ulnar nerve, roots C8–T1. |
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The dual nerve supply means median or ulnar nerve injuries can affect different lumbricals. Loss of the ulnar lumbricals may lead to a claw-like finger posture, which is a nerve sign that needs referral, not a massage problem.
Section 06 of 20
Blood Supply
| Blood | Superficial and deep palmar arches, palmar metacarpal arteries, and common palmar digital arteries. |
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Section 07 of 20
Pictures and Visual Anatomy
An anatomical image for this section will be added when verified source media becomes available.
Section 08 of 20
Functional Movement
The lumbricals are used when writing, typing, playing instruments, threading a needle, and holding a cup or a tool with the fingers extended. They allow the finger tips to move while the knuckles stay bent.
Section 09 of 20
Synergists and Antagonists
Synergists: the palmar and dorsal interossei (metacarpophalangeal flexion and interphalangeal extension) and, for finger control, flexor digitorum profundus and extensor digitorum. Antagonists: extensor digitorum (metacarpophalangeal extension) and flexor digitorum profundus and superficialis (interphalangeal flexion).
Section 10 of 20
Palpation and Location
Client position and technique
The lumbricals are deep in the palm and cannot be felt separately. With the client's palm up and the wrist supported, gently locate the flexor tendons near the metacarpal heads and the web spaces. Ask the client to bend the knuckles while keeping the finger tips straight to feel the deep tissue of the palm and web spaces engage.
Protect nearby structures
The palm contains the median and ulnar nerves, palmar arteries, and flexor tendon sheaths. Use light to moderate pressure, avoid pressing over a tender nodule, wound, or swollen sheath, and stop if the client reports tingling, numbness, or sharp pain.
Section 11 of 20
Massage Therapy Relevance
Repeated fine finger work in typing, writing, music, and crafts loads the intrinsic hand muscles, and tightness or fatigue in the palm can accompany hand and finger discomfort. Many nerve, tendon, and joint problems can cause similar symptoms.
Section 12 of 20
Dysfunction: What Happens When Movement Goes Wrong
Changes in how a muscle works can change how a joint moves. The points below describe possibilities that may be associated with altered muscle function; they are not diagnoses, and one muscle is never assumed to be the sole cause of a problem.
When the muscle is weak
Weakness may reduce fine finger control and may be associated with a claw-like finger posture when the nerve supply is affected.
When it is tight or shortened
Tightness may be associated with a stiff, cramped palm and limited finger extension with the knuckles bent.
When it is overused
Repeated fine finger work may overload the small muscles and may contribute to palm ache and finger fatigue.
When it is strained
A strain may cause deep palm pain with gripping; tendon and nerve problems can look similar.
When it is inhibited or others compensate
Reduced activation may be associated with more work by the long finger flexors and extensors and clumsy finger control.
When it does not coordinate well with synergists and antagonists
Poor coordination with the interossei and the long finger muscles may alter finger posture and may be associated with hand and finger symptoms.
Section 13 of 20
Conditions, Pathologies, and Pain Relationships
Intrinsic hand overuse
Repetitive fine finger work may be associated with palm ache and finger fatigue, but tendon and nerve problems can look similar.
Ulnar nerve injury and claw hand
Weakness of the third and fourth lumbricals and the interossei may leave the ring and little fingers extended at the knuckle and flexed at the finger joints.
Carpal tunnel syndrome
Median nerve compression can eventually affect the first and second lumbricals and cause numbness and tingling in the thumb, index, and middle fingers.
Differential considerations
Trigger finger, Dupuytren contracture, flexor tendon injury, arthritis, and cervical radiculopathy can also cause palm and finger symptoms.
Section 14 of 20
Example Clinical Relationship
A musician reports deep palm ache and fatigue when playing long passages that need bent knuckles and straight fingers. The lumbricals and other intrinsic hand muscles may be involved, and the pattern may be associated with overuse, but tendon, nerve, and joint problems can look similar. Gentle palm work may support comfort, while a hot swollen finger, sudden weakness, or progressive numbness needs referral.
Section 15 of 20
Massage and Treatment Approaches
For healthy, non-acute tissue, position the client supine or seated with the forearm supported and palm up. Begin with light effleurage on the palm, use gentle thumb kneading between the metacarpal heads, and add gentle finger and knuckle mobilization within comfort.
| Movement | Use gentle passive and active finger flexion and extension in the pen-holding position; do not force stretch. |
|---|---|
| Regional work | Consider the interossei, thenar and hypothenar muscles, the forearm flexors and extensors, and the palmar fascia when assessment supports it. |
| Avoid | Deep pressure over the carpal tunnel and palmar nerves, wounds, nodules, or swollen or hot finger sheaths. |
Section 16 of 20
Precautions and Contraindications
Precautions and contraindications
- Recent hand injury, fracture, surgery, or open wound.
- Use caution with rheumatoid arthritis, Dupuytren contracture, or severe osteoarthritis of the fingers.
- Use caution with anticoagulant use or easy bruising.
- Stop if pressure causes numbness, tingling, or sharp pain.
Section 17 of 20
Red Flags and When to Refer
Red flags and referral
- A hot, red, swollen finger or palm with fever, especially with pain on straightening the finger (possible infection).
- Sudden weakness, loss of finger control, or a claw-like posture of the fingers.
- Progressive numbness in the hand or fingers, or loss of sensation.
- Hand or arm pain with neck pain, chest pain, or shortness of breath.
Section 18 of 20
Study Summary
Attachments
Origin: flexor digitorum profundus tendons in the palm. Insertion: radial side of the extensor expansion of fingers 2–5.
Actions
Flex the metacarpophalangeal joints and extend the interphalangeal joints.
Supply
Median nerve (lumbricals 1–2) and ulnar nerve deep branch (lumbricals 3–4), C8–T1; palmar arches.
Section 19 of 20
Instructor Narration
Open narration transcript
The lumbricals are four small worm-like muscles in the palm. They are unusual because they arise from tendons instead of bone.
They arise from the flexor digitorum profundus tendons in the palm and insert on the radial side of the extensor expansion of the four fingers.
They flex the metacarpophalangeal joints and extend the interphalangeal joints at the same time. The interossei help them, and extensor digitorum and the long finger flexors oppose part of the movement.
The median nerve supplies the first and second lumbricals, the deep branch of the ulnar nerve supplies the third and fourth, and the palmar arches provide the blood supply.
They are deep and cannot be felt separately, so work gently in the palm and web spaces and avoid pressure over the palmar nerves and sheaths.
Overuse, ulnar nerve injury with claw hand, carpal tunnel syndrome, and tendon problems can overlap. Refer a hot swollen finger or palm, sudden weakness, a claw posture, or progressive numbness.
Remember: flexor digitorum profundus tendons to the extensor expansion; knuckle flexion with finger extension; median and ulnar nerves.
Section 20 of 20