Muscle · Elbow

Extensor digitorum

Musculus extensor digitorum

The muscle that opens the hand. It sits in the middle of the back of the forearm and sends four tendons across the back of the hand — the cords you can see standing up under the skin when you spread your fingers. Those tendons are linked to one another by small bands, which is why lifting the ring finger alone is so awkward. It arises from the shared extensor tendon at the outer elbow, so it belongs to the same tissue involved in tennis elbow, and it flattens into a hood over each finger that the small hand muscles also pull on — a shared arrangement that lets the fingers straighten fully.