Extensor Indicis Proprius Wrist Bursa

bursa tendinis extensoris indicis proprii

The extensor indicis tendon runs through the fourth extensor compartment of the wrist inside a synovial sheath it shares with the four extensor digitorum tendons. The sheath lets these tendons glide beneath the extensor retinaculum, and it is often inflamed in rheumatoid arthritis, which can lead to tendon rupture.

Anatomical Data

Boundaries & Contents

Location	Back of the wrist, in the fourth extensor compartment beside Lister tubercle
Boundaries	Dorsal distal radius (floor) Extensor retinaculum (roof)
Contents	Extensor indicis tendon Four extensor digitorum tendons (sharing the sheath) Terminal branch of the posterior interosseous nerve (on the floor of the compartment)

Biomechanics

Function & Actions

Lets the index and finger extensor tendons glide under the extensor retinaculum. Inflammation of this shared sheath is common in rheumatoid arthritis.

Clinical Relevance

Clinical Notes

EIP wrist bursitis causes dorsal wrist pain with independent index finger extension. It is part of the fourth extensor compartment tenosynovitis syndrome seen in inflammatory arthropathy. Ultrasound identifies fluid around the EIP tendon at the retinaculum level. Fourth compartment decompression addresses both EIP and EDC tendon sheath pathology.

Pathology

Common Injuries & Conditions

Fourth Extensor Compartment Bursitis

Bursal inflammation around the EIP tendon at the wrist producing dorsal wrist pain with index finger extension, a feature of inflammatory tenosynovitis managed with injection and compartment release.

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