Thumb Movements and Muscle Anatomy

Thumb Extension, Abduction, Adduction, and Opposition

• Muscles Involved in Thumb Extension: Extensor pollicis longus, Extensor pollicis brevis
• Range of Motion for Thumb Extension: 60° – 70° to 0° (metacarpophalangeal), 90° – 0° (interphalangeal)
• Muscles Involved in Thumb Abduction: Abductor pollicis longus, Abductor pollicis brevis
• Range of Motion for Thumb Abduction: 0° to 40°–50° (metacarpophalangeal)
• Muscles Involved in Thumb Adduction: Adductor pollicis
• Range of Motion for Thumb Adduction: 40°–50° to 0°
• Muscles Involved in Thumb Opposition: Opponens pollicis, Opponens digiti minimi
• Range of Motion for Thumb Opposition: Opposes (medially rotates and flexes) carpometacarpal and metacarpophalangeal joints of the thumb.

Primary Muscles: Detailed Anatomy, Origin, Insertion, Nerve Supply, and Action

Extensor Pollicis Longus

• Origin: Middle third of posterior ulna
• Insertion: Base of distal phalanx of thumb
• Nerve Supply: Radial nerve
• Action: Extends interphalangeal and metacarpophalangeal joints of thumb

Extensor Pollicis Brevis

• Origin: Posterior surfaces of radius and interosseous membrane
• Insertion: Base of proximal phalanx of thumb
• Nerve Supply: Radial nerve
• Action: Extends proximal phalanx of thumb at the carpometacarpal joint

Abductor Pollicis Longus

• Origin: Upper posterior surface of ulna and middle third of posterior surface of radius
• Insertion: Over tendons of radial extensors, brachioradialis to the base of 1st metacarpal and trapezium
• Nerve Supply: Radial nerve
• Action: Abducts and extends thumb at carpometacarpal joint

Abductor Pollicis Brevis

• Origin: Tubercle of scaphoid and flexor retinaculum
• Insertion: Radial sesamoid of proximal phalanx of thumb and tendon of extensor pollicis longus
• Nerve Supply: Median nerve
• Action: Abducts thumb at the metacarpophalangeal and carpometacarpal joints

Adductor Pollicis

• Origin: Oblique head: base of 2nd and 3rd metacarpals, trapezoid, and capitate; Transverse head: palmar border and shaft of 3rd metacarpal
• Insertion: Ulnar side of base of proximal phalanx of thumb and tendon of extensor pollicis longus
• Nerve Supply: Ulnar nerve
• Action: Adducts carpometacarpal joint of thumb

Opponens Pollicis

• Origin: Flexor retinaculum and tubercle of trapezium
• Insertion: Whole of radial border of 1st metacarpal
• Nerve Supply: Median nerve
• Action: Opposes (medially rotates and flexes) carpometacarpal and metacarpophalangeal joints of thumb

Opponens Digiti Minimi

• Origin: Flexor retinaculum and hook of hamate
• Insertion: Ulnar border of shaft of 5th metacarpal
• Nerve Supply: Ulnar nerve
• Action: Opposes (flexes and laterally rotates) carpometacarpal and metacarpophalangeal joints of little finger

Explore the critical functions and anatomy of the muscles involved in thumb extension, abduction, adduction, and opposition. This quiz includes details on the range of motion and specific muscles' origins, insertions, and actions. Perfect for students of anatomy and physiotherapy.