Third Palmar Interosseous Muscle

Origin

The third palmar interosseous muscle originates from the palmar aspect of fifth metacarpal bone.

Insertion

The fibers of the third palmar interosseous muscle travel inferiorly to the little finger and insert, via a short tendon, onto the:

- lateral aspect of the base of the proximal phalanx of little finger;

- extensor expansion of little finger.

Key Features & Anatomical Relations

The third palmar interosseous muscle is found in the interosseous compartment of the hand. It is a short, unipennate skeletal muscle. It is located:

- anterior to the fifth metacarpal bone and the fourth dorsal interosseous muscle of hand;

- posterior to the fourth lumbrical muscle of hand.

Actions & Testing

The third palmar interosseous muscle is involved in multiple actions:

- adducts the proximal phalanx of little finger (i.e., draws it towards the longitudinal axial line of the middle finger) at the fifth metacarpophalangeal joint;

- simultaneously flexes the fifth metacarpophalangeal joint and extends the interphalangeal joints of the little finger, which occurs when the fourth lumbrical muscle of hand contracts simultaneously with it.

The third palmar interosseous muscle can be tested by adducting the proximal phalanx of little finger at the fifth metacarpophalangeal joint against resistance (Standring, 2016).

References

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