Learning Objectives

By the end of this article, the learner should be able to:

• Describe the anatomical location of the six extensor tendon compartments of the wrist
• Identify the tendons contained within each compartment
• Explain the relationship of the extensor compartments to surface landmarks, including the anatomical snuffbox
• Recognise key clinical correlations, particularly De Quervain’s tenosynovitis

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Introduction

The extensor tendon compartments of the wrist are six fibro-osseous tunnels located on the posterior (dorsal) aspect of the wrist. These compartments transmit the long extensor tendons from the forearm into the hand.

Each compartment is:

• Lined internally by a synovial sheath, allowing smooth tendon movement
• Separated from adjacent compartments by fibrous septa
• Secured in place by the extensor retinaculum

Together, these compartments maintain tendon alignment during wrist and finger extension while preventing bowstringing.

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The Extensor Compartments

Compartment 1

Location: Radial (lateral) aspect of the wrist

Contents:

• Abductor pollicis longus (APL)
• Extensor pollicis brevis (EPB)

These tendons form the lateral border of the anatomical snuffbox.

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Clinical Correlation

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De Quervain’s Tenosynovitis

De Quervain’s tenosynovitis is an inflammatory condition affecting the tendons of the first extensor compartment.

Epidemiology:

• Most common in women aged 30–50 years
• Associated with repetitive wrist and thumb movements

Clinical Features:

• Pain and swelling at the radial aspect of the wrist
• Pain worsened by grasping, pinching, or thumb movement
• Thickening of the tendon sheath may be palpable

Management:

• Conservative: activity modification, wrist/thumb splinting
• Steroid injections: effective in most patients
• Surgical decompression: indicated for refractory cases

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Compartment 2

Contents:

• Extensor carpi radialis longus (ECRL)
• Extensor carpi radialis brevis (ECRB)

This compartment lies radial to Lister’s tubercle, a bony prominence on the distal radius.

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Compartment 3

Contents:

• Extensor pollicis longus (EPL)

The EPL tendon curves around Lister’s tubercle, using it as a pulley, and forms the medial border of the anatomical snuffbox.

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Compartment 4

Contents:

• Extensor digitorum
• Extensor indicis

This is the largest extensor compartment and supplies extension to the fingers.

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Compartment 5

Contents:

• Extensor digiti minimi

This tendon travels to the little finger, allowing independent extension.

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Compartment 6

Location: Ulnar (medial) aspect of the wrist

Contents:

• Extensor carpi ulnaris (ECU)

The ECU tendon plays a key role in ulnar deviation and wrist stabilisation.

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Summary Table