The muscle located between the thumb and forefinger is the first dorsal interosseous muscle.
This muscle plays a crucial role in hand function and can be easily identified by observing the dorsal (back) side of the hand. When you abduct your index finger (move it away from the middle finger), you'll notice a bulge forming between your thumb and index finger – that's the first dorsal interosseous muscle contracting.
Location and Function
- Location: Found on the back of the hand, between the thumb and index finger. It originates from the adjacent sides of the first and second metacarpal bones (bones of the hand).
- Function: Primarily responsible for the abduction of the index finger. Abduction refers to moving a body part away from the midline of the body or, in the case of fingers, away from the middle finger. It also assists in flexion at the metacarpophalangeal joint (the knuckle joint where the fingers connect to the hand).
Clinical Significance
The first dorsal interosseous muscle can be affected by various conditions:
- Cubital Tunnel Syndrome: In severe cases, damage to the ulnar nerve (which innervates this muscle) can lead to atrophy (shrinkage) of the first dorsal interosseous. This makes it a useful indicator for diagnosing the severity of the condition.
- Wasting/Atrophy: Atrophy of this muscle can also occur due to other nerve injuries or disuse.
- Muscle Strain: Like any muscle, it can be strained due to overuse or injury.
Identification
You can easily palpate (feel) the first dorsal interosseous muscle by placing your opposite hand on the back of your hand, between your thumb and index finger, and then abducting your index finger against resistance. You should feel the muscle contracting and becoming more prominent.
