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In Depth: Deep Muscles

Whereas the larger exterior muscles of the arm provide the most profound movements, such as the bending of the elbow and wrist, the smaller deep muscles of the arm perform many functions, such as twisting the wrist or moving the fingers. It is because of these muscles that the wrist and fingers can perform such detailed tasks.

Some deep muscles of the arm include:

  • Flexor carpi radialis: This muscle travels down and across the forearm from the elbow to the wrist to bend the hand outward.
  • Flexor digitorum profundis: This long forearm muscle flexes the wrist and fingers.
  • Pronator teres: This muscle crosses the forearm under the brachioradialis and helps turn the hand so that the palm faces downward.
  • Abductor pollicis longus: This forearm muscle helps abduct the wrist and the thumb. It is important in holding small objects, such as a pencil.
  • Extensor pollicis brevis: Another important thumb muscle, this one acts in conjunction with the abductor pollicis longus to extend and bend the thumb outward.
  • Supinator: This muscle near the elbow helps the bicep muscle to turn the hand palm-side up.
  • Anconeus: Also near the elbow, this small muscle aids in extending the elbow and stabilizes the elbow joint.

Because the deep muscles of the arm perform such small and specialized functions that play a huge role in daily tasks, they are prone to injury. Problems with these muscles and their associated tendons can limit a person’s joint dexterity as well as cause pain and irritation.

Repetitive stress injuries, due to activities such as playing sports or using a keyboard, can cause inflammation and pain. Collectively, these injuries are known as tendonitis. If the tendon on the outside of the joint is affected, it is called “tennis elbow.” If it is the tendon on the inside of the elbow, the condition is known as “golfer’s elbow.”

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