Flexor Pollicis Longus Muscle, Anterior View

Description

Running along the volar aspect of the left forearm and wrist, the flexor pollicis longus (FPL) is traced from its muscular belly to the long tendon that passes into the palm and continues to the thumb. Distally, the tendon courses deep to the flexor retinaculum at the carpal tunnel region, then travels along the first ray to insert on the base of the distal phalanx of the pollex, anterior to the first metacarpal and phalanges. Carpal bones, metacarpals, and phalanges are shown in anatomical alignment, with the thumb positioned laterally and the interphalangeal and metacarpophalangeal joints rendered as clear bony landmarks. Clean tendon trajectory. FPL matters because it is the primary flexor of the thumb interphalangeal joint, and its tendon glide is tightly constrained at the wrist and within the digital flexor sheath. That relationship underpins common problems such as flexor pollicis longus tenosynovitis (trigger thumb) and attritional or traumatic rupture, including postoperative complications after volar plate fixation of distal radius fractures where prominent hardware can abrade flexor tendons. For surgical teaching, the line of pull and insertion explain why loss of IP flexion persists even when thenar muscles remain intact, and why isolated anterior interosseous nerve palsy produces weakness of FPL without sensory loss. Use this artwork for upper limb anatomy and hand surgery lectures, occupational therapy and physiotherapy modules on thumb biomechanics, or textbook figures describing extrinsic thumb flexors and tendon paths through the carpal tunnel. It also suits patient-facing education in clinics discussing trigger thumb release, tendon repair, or rehabilitation after distal radius fixation. Anatomical accuracy verified by SciePro's Medical Advisory Board.