The small muscles of the hand

What it does

The interossei sit between the metacarpals and spread and close the fingers. The lumbricals are worm-like muscles attached to the tendons of the finger flexors. Together they let you bend at the knuckles while keeping the fingers straight, the position you use to write or play an instrument.

Why it matters

Their fine control lets you play the piano, sew or type quickly. When they weaken, the hand slowly loses its delicate skills before it loses strength.

Nearby

• The palm bones
• The finger bones
• The "funny bone"
• The deep finger flexor

Read more

• Lumbricals and interossei — Wikipedia