Thumb Articulations

Carpometacarpal

Flexion

Bending the joint resulting in a decrease of angle; moving the bone below the thumb toward the hand and slightly Forward.


Extension

Straightening the joint resulting in an increase of angle; moving the bone below the thumb away from the hand and slightly back.


Adduction

Medial movement toward the midline of the body; moving the bone below the thumb toward the back of the wrist.


Abduction

Lateral movement away from the midline of the body; moving the bone below the thumb toward the front of the wrist.

  • Abductor pollicis longus
  • Abductor pollicis brevis

Opposition

Diagonal movement of the thumb across the palm of the hand making contact with the fingers.


Metacarpophalangeal


Flexion

Bending the joint resulting in a decrease of angle; moving the base of the thumb toward the heel of the hand.


Extension

Straightening the joint resulting in an increase of angle; moving the base of the thumb away from the heel of the hand.


Adduction

Medial movement toward the midline of the body; slight movement of the base of the thumb toward the back of the hand.

  • Adductor pollicis
  • 1st palmar interosseous

Abduction

Lateral movement away from the midline of the body; slight movement of the base of the thumb away from the back of the hand.

  • Abductor pollicis brevis

Interphalangeal


Flexion

Bending the joint resulting in a decrease of angle; moving the distal segments of the thumb toward the base of the thumb.


Extension / Hyperextension

Straightening the joint resulting in an increase of angle; moving the distal segments of the thumb away from the base of the thumb.


Notes

See Wrist for midcarpal joints. Also see Fingers.


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