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Palmaris Longus (PL)

Key Points:
• Flexes the wrist.
• Extrinsic muscle.
• Present in about 14% of the population.

Muscle Function:

Primary: Tenses the palmar fascia and flexes the wrist.
Secondary: May assist in flexion of the elbow.

Palpation: Tendon can often be visualized as the most superficial at the wrist.

Strength Testing: Position – palm up. Stabilize – the hand while it is cupped and in wrist flexion. Resist – against wrist flexion (in the direction of wrist extension. Resistance is applied towards opening the hand. Or ask the patient to palmarly flex the wrist and then ask them to touch the small finger to the thumb and observe the tendon of the palmaris longus contract with this thumb to small finger maneuver. Testing is generally not graded formally and the exam is noted as either present or absent palmaris longus muscle.

Possible Substitutions: None.

Relevant Anatomy:

• Roots: C7, C8.
• Nerve: Median nerve.
• Innervation Route: C7, C8 → median nerve → flexor carpi radialis and palmaris longus branch → palmaris longus branch.

Origins: Common flexor tendon from medial epicondyle of humerus and deep antebrachial fascia.

Insertion: Flexor retinaculum and palmar aponeurosis.