Topic Overview

✋ Wrist (Radiocarpal) Joint

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Type

• Ellipsoid (condyloid) synovial joint.

• Allows movements in two axes — flexion/extension and abduction/adduction (circumduction as a combination).

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Articular Surfaces

Structure	Surface Description
Proximal (upper)	Distal end of radius and articular disc of inferior radioulnar joint (triangular fibrocartilage)
Distal (lower)	Proximal surfaces of scaphoid, lunate, and triquetral bones (carpal bones)

👉 The ulna does not participate directly — its articular disc intervenes.

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Joint Capsule

• Thin and loose → allows free movement.

• Attached:

  • Above: Margins of articular surface of radius and disc.

  • Below: Around proximal carpal row (scaphoid, lunate, triquetral).

• Lined by synovial membrane.

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Ligaments

Ligament	Attachments	Function
Palmar radiocarpal	From anterior distal radius → anterior carpal bones	Limits wrist extension
Dorsal radiocarpal	From posterior radius → dorsal carpus	Limits wrist flexion
Ulnar collateral	From ulnar styloid → triquetral & pisiform	Prevents excessive abduction
Radial collateral	From radial styloid → scaphoid	Prevents excessive adduction

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Synovial Membrane

• Lines inner surface of capsule.

• Does not communicate with midcarpal joint cavity.

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Relations

Anteriorly	Posteriorly
Tendons of FCR, FDS, FDP, FPL; median & ulnar nerves; radial & ulnar arteries	Extensor tendons of forearm enclosed by synovial sheaths

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Nerve Supply

• Anterior interosseous branch of median nerve

• Posterior interosseous branch of radial nerve

• Deep branch of ulnar nerve

(Hilton’s law — nerves supplying muscles acting on the joint also supply the joint.)

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Blood Supply

• Dorsal and palmar carpal branches of radial and ulnar arteries, with anterior interosseous artery.

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🔄 Movements at Wrist Joint

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Movement	Range (°)	Muscles Producing Movement
Flexion	0–80°	FCR, FCU, FDS, FDP, FPL
Extension	0–70°	ECRL, ECRB, ECU
Abduction (radial deviation)	0–20°	FCR, ECRL, ECRB
Adduction (ulnar deviation)	0–45°	FCU, ECU
Circumduction	Composite	Sequential combination of above movements

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Axes of Movement

• Flexion–extension: Transverse axis.

• Abduction–adduction: Anteroposterior axis.

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Stability Factors

• Strong collateral and capsular ligaments.

• Interlocking carpal bones.

• Balanced muscle tone of flexors and extensors.

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🧠 Dissection of Wrist Joint

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Steps

1. Place forearm prone; make a transverse incision about 3 cm above the wrist crease and another across the dorsum of hand.

2. Reflect skin and superficial fascia to expose extensor and flexor tendons.

3. Identify:

   • Radial artery (lateral) and ulnar artery (medial).

   • Median nerve anterior to wrist joint (beneath flexor retinaculum).

4. Reflect extensor retinaculum and tendons to reveal dorsal aspect of capsule.

5. Identify dorsal radiocarpal and radial collateral ligaments.

6. Anteriorly, expose palmar radiocarpal and ulnar collateral ligaments.

7. Carefully incise capsule → observe:

   • Convex radius/disc above, concave scaphoid–lunate–triquetral below.

   • Synovial membrane and meniscoid folds.

8. Move wrist to demonstrate flexion, extension, and circumduction.

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🏥 Clinical Anatomy of Wrist Joint

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1. Colles’ Fracture

• Fracture of distal radius about 2.5 cm above wrist.

• Fragment displaced dorsally → “Dinner-fork deformity.”

• Common after a fall on outstretched hand (especially in elderly women).

• May cause median nerve compression or radiocarpal stiffness.

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2. Smith’s Fracture (Reverse Colles’)

• Fracture of distal radius with palmar displacement of fragment → “Garden-spade deformity.”

• Occurs in fall on dorsum of hand.

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3. Barton's Fracture

• Intra-articular fracture of distal radius extending into wrist joint → may cause radiocarpal dislocation.

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4. Scaphoid Fracture

• Commonest carpal fracture; tenderness in anatomical snuffbox.

• Blood supply (radial artery) runs distal-to-proximal → risk of avascular necrosis of proximal fragment.

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5. Wrist Sprain

• Stretch injury of ligaments during forceful dorsiflexion.

• Pain and restricted movement, but no fracture on X-ray.

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6. Carpal Instability

• Results from ligamentous injury between scaphoid, lunate, and triquetral → abnormal alignment, pain, “clunk” on movement.

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7. Ganglion Cyst

• Cystic swelling from synovial sheath or joint capsule, commonly on dorsum of wrist.

• Contains clear jelly-like fluid; often asymptomatic or painful during extension.

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8. Radiocarpal Arthritis

• Inflammation or degeneration (as in rheumatoid arthritis) → swelling, stiffness, pain on flexion/extension.

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9. Carpal Tunnel Syndrome (indirect effect)

• Swelling at wrist (tenosynovitis or arthritis) compresses median nerve → numbness in lateral 3½ digits and thenar weakness.