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Scapholunate Joint Space

articulatio scapholunata

The scapholunate joint is the articulation between the medial surface of the scaphoid and the lateral surface of the lunate in the proximal carpal row. The two bones are bound by the scapholunate interosseous ligament on their dorsal and palmar surfaces, with a fibrocartilaginous central connection. Normal scapholunate gap measures 2-3 mm on PA wrist radiograph; a gap exceeding 3 mm or greater is abnormal and suggests ligament injury.

Region: Hand & Wrist

Clinical Relevance

Clinical Notes

The scapholunate joint is the most commonly injured intercarpal articulation. Scapholunate dissociation from ligament disruption produces dorsal intercalated segment instability (DISI) where the lunate tilts into dorsiflexion. The joint is assessed by the scapholunate gap on radiograph, the Terry Thomas sign (widened gap on clenched fist PA view), and the scaphoid ring sign (foreshortening from scaphoid flexion). MRI arthrography provides direct ligament assessment. Arthroscopic ligament repair or reconstruction is performed depending on acuity and ligament quality.

Pathology

Common Injuries & Conditions

Scapholunate Dissociation

Disruption of the scapholunate interosseous ligament, typically from a fall on an outstretched hand, produces widening of the scapholunate gap (Terry Thomas sign on X-ray), DISI collapse pattern, wrist pain, and loss of grip, managed by ligament repair acutely or reconstruction for chronic cases.

SLAC Wrist

Progressive scapholunate advanced collapse arthritis follows untreated scapholunate dissociation as the malpositioned scaphoid develops arthrosis first with the radial styloid then the capitate, managed with radial styloidectomy, four-corner fusion, or total wrist fusion in advanced disease.