Normal Intercarpal Joint Space Size on Radiography
The intercarpal joint spaces are the narrow articulations between adjacent carpal bones of the wrist, maintained by a complex network of intrinsic and extrinsic ligaments. Accurate measurement of these spaces on plain radiographs is essential for identifying ligamentous injury, inflammatory arthritis, and post-traumatic carpal collapse. Even subtle asymmetric narrowing or widening can signal significant underlying pathology.
Normal Reference Values
| Orientation | Measurement |
|---|---|
| Posteroanterior, Lateral | 1.5-2.0 mm |
Clinical Significance
A normal intercarpal joint space of 1.5–2.0 mm reflects intact cartilage and ligamentous support. Widening beyond this range — particularly at the scapholunate interval — raises concern for ligamentous disruption. A scapholunate gap exceeding 3 mm (the "Terry Thomas sign") is a well-recognized indicator of scapholunate dissociation. Conversely, joint space narrowing below 1.5 mm suggests cartilage loss from inflammatory or degenerative arthritis.
Assessment should always include comparison with the contralateral wrist and correlation with clinical findings, as mild asymmetry can be positional. Stress views (radial/ulnar deviation, clenched-fist) may unmask dynamic instability not apparent on neutral radiographs.
- Scapholunate dissociation — widened scapholunate space, DISI deformity
- Lunotriquetral instability — subtle narrowing or overlap at the lunotriquetral interval
- Rheumatoid arthritis — diffuse symmetrical intercarpal joint space narrowing
- Calcium pyrophosphate deposition (CPPD) — chondrocalcinosis with progressive joint space loss
- Post-traumatic osteoarthritis — focal narrowing following carpal fractures
Reference: Müller TB. Normal Findings in Radiology. Thieme. (2000).
Imaging Notes
Intercarpal joint spaces are best evaluated on a posteroanterior (PA) radiograph obtained with the wrist in neutral position, the forearm pronated, and the hand flat on the detector — minimizing rotational distortion. The lateral view complements the PA by assessing carpal alignment and detecting dorsal or volar intercalated segment instability (DISI/VISI). Consistent tube-to-detector distance and patient positioning are critical, as even slight wrist flexion or rotation can artifactually alter apparent joint space width.
Measurements should be taken at the midpoint of each intercarpal articulation using digital calipers on PACS. Comparison of the same joint space bilaterally under identical positioning increases diagnostic confidence when asymmetry is suspected.