Thumb

The Thumb: The Pollex

Bone Structure Muscle Attachments To Thumb
Intrinsic (thenar)

Abductor PollicisBrevis
• Abducts the Thumb basal (carpometacarpal) Joint along with other muscles which palmar abduct and radial abduct the basal joint, and extends the thumb interphalangeal Joint
Adductor Pollicis (Tendon)
• radially adducts the thumb basal joint along with other muscles which radially adduct the basal joint, and extends the thumb’s interphalangeal Joint
First Dorsal Interosseous
• flexes, radially deviates (abducts) and pronates the index MCP joint and radially adducts the thumb basal joint along with other muscles which radially adduct the basal joint. Also (weakly) extends the index PIP and DIP joints
Flexor Pollicis Brevis
• Flexes the thumb MCP joint and flexes/pronates the basal joint along with other muscles which produce thumb opposition

Opponens Pollicis
• flexes and pronates the basal joint along with other muscles which produce thumb opposition
Extrinsic
Abductor Pollicis Longus (Tendon)
• Abducts the thumb basal joint, along with other muscles which radially abduct the thumb. Also radially deviatesthe wrist along with other muscles which produce wrist radial abduction
Extensor Pollicis Brevis (Tendon)
• Extends the thumb MCP joint and weakly abducts the thumb basal joint, along with other muscles which produce radial and palmar abduction
Extensor Pollicis Longus (Tendon)
• Extends the thumb Interphalangeal Joint
Flexor Pollicis Longus (Tendon)
• Flexes the thumb Interphalangeal Joint (primary) and Metacarpophalangeal Joint (weak)
Joints In The Thumb • Interphalangeal Joint (IP)
• Metacarpophalangeal Joint (MCP) o These two joints are Hinge Joints which essentially provide the same function as a door.
• Carpometacarpal Joint (CMC) o This joint in the thumb, is a Sattle Joint; meaning there is a sattle like bone that is being wrapped around by a “U” shaped bone to allowed for a back and forth directive