Tendon sheath of extensor pollicis longus
Vagina tendinis extensoris longi pollicis
- Latin synonym: Vagina tendinis musculi extensoris pollicis longi
- Synonym: Tendinous sheath of extensor pollicis longus muscle
- Related terms: Tendinous sheath of extensor pollicis longus
Definition
The tendon sheath of extensor pollicis longus (EPL) is a synovial sheath that encloses the EPL tendon as it passes obliquely across the dorsum of the wrist through the third dorsal compartment, beneath the extensor retinaculum.
The tendon curves medially around the dorsal tubercle of the radius, which acts as a pulley, redirecting its course toward the thumb. The tendon sheath extends from just proximal to the wrist joint to the base of the distal phalanx of the thumb, facilitating smooth and friction-free movement along this angled path.
Within the third dorsal compartment, the sheath allows the EPL tendon to glide over the bony surface of the radius and beneath the retinaculum during extension of the thumb and wrist.
Please note that the extensor retinaculum divides the dorsal wrist into six fibro-osseous compartments, each containing specific extensor tendons and their synovial sheaths; the EPL tendon exclusively occupies the third compartment, situated between the second (extensor carpi radialis longus and brevis) and fourth (extensor digitorum and extensor indicis) compartments.
References
Gray, H. (2016) Gray’s Anatomy: The Anatomical Basis of Clinical Practice. 41st edn. Edited by S. Standring. New York: Elsevier. Chapter 50: Wrist and hand, pp. 879.
Drake, R.L., Vogl, A.W. and Mitchell, A.W.M. (2009). ‘Chapter 7: Hand’ in Gray’s anatomy for Students. (2nd ed.) Philadelphia PA 19103-2899: Elsevier, pp. 757; Fig. 7.95.
MickeyMed. (n.d.). Extensor retinaculum of hand. Available at: https://www.mickeymed.com/article/extensorretinaculumofhand (Accessed: 7 January 2026).
