The flexor pollicis longus (FPL) distal tendon inserts into the base of the distal phalanx of the thumb within zone 1 and zone 2 of the flexor sheath system. In zone 2 it runs within the fibro-osseous sheath between the A1 and oblique pulleys; in zone 1 it exits the oblique pulley to insert at the distal phalanx. The FPL is the only extrinsic flexor of the thumb IP joint.
| Muscle | |
|---|---|
| Attachment | Palmar base of the distal phalanx of the thumb |
Flexes the thumb interphalangeal joint
FPL tendon laceration in zone 1-2 (the thumb equivalent of jersey finger) produces inability to flex the thumb IP joint. FPL avulsion at the distal phalanx base is rare and presents with a palpable tendon mass at the MCP or wrist if the tendon retracts proximally. Repair principles mirror FDP zone 2 repair: early primary repair with core and epitenon sutures within the fibro-osseous sheath for zone 2 injuries; bone anchor reattachment for zone 1 distal avulsions. The FPL runs in its own synovial sheath (the radial bursa) through the carpal tunnel, which often communicates with the ulnar bursa. Trigger thumb, from a tendon nodule catching at the A1 pulley, causes locking of the IP joint and is treated with injection or A1 pulley release; a congenital form in young children may resolve spontaneously.
Forced hyperextension of the thumb IP joint avulses the FPL from the distal phalanx base producing thumb jersey finger with inability to actively flex the IP joint; the retracted tendon may be palpable in the palm or wrist if retraction is complete, requiring urgent repair within 10 days before muscle fibrosis and tendon shortening prevent anatomic reattachment.
FPL nodule or thickened sheath catching at the A1 pulley producing painful clicking or locking of the thumb IP joint, managed with injection and A1 pulley release.
This website uses cookies to enhance your experience. Some are essential for site functionality, while others help us analyze and improve your usage experience. Please review your options and make your choice.
If you are under 16 years old, please ensure that you have received consent from your parent or guardian for any non-essential cookies.
Your privacy is important to us. You can adjust your cookie settings at any time. For more information about how we use data, please read our privacy policy. You may change your preferences at any time by clicking on the settings button below.
Note that if you choose to disable some types of cookies, it may impact your experience of the site and the services we are able to offer.
Some required resources have been blocked, which can affect third-party services and may cause the site to not function properly.
This website uses cookies to enhance your browsing experience and ensure the site functions properly. By continuing to use this site, you acknowledge and accept our use of cookies.
