Normal Capitolunate Angle Size on Radiography
The capitolunate angle is a geometric measurement on the lateral wrist radiograph that quantifies the angular relationship between the capitate and lunate bones. It serves as a sensitive indicator of carpal alignment and mid-carpal stability. Accurate assessment of this angle is essential in evaluating wrist pain, trauma, and suspected carpal instability syndromes.
Normal Reference Values
| Orientation | Measurement |
|---|---|
| Lateral | -15-15¡ |
Clinical Significance
A normal capitolunate angle lies within -15° to +15° on the lateral radiograph. Values outside this range suggest disruption of the normal carpal arc and should prompt further clinical and imaging evaluation. Dorsal intercalated segment instability (DISI) typically produces a positive capitolunate angle exceeding +15°, while volar intercalated segment instability (VISI) produces a negative angle beyond -15°.
Carpal instability may result from ligamentous injury, fracture non-union (e.g., scaphoid), inflammatory arthropathy, or post-traumatic deformity. An abnormal capitolunate angle often accompanies an abnormal scapholunate or lunotriquetral angle, and these measurements should be interpreted together rather than in isolation. Positioning errors and wrist rotation can introduce significant measurement variability, so a strict lateral projection is mandatory.
- DISI pattern — scapholunate ligament tear, scaphoid non-union advanced collapse (SNAC)
- VISI pattern — lunotriquetral ligament injury, ulnar-sided instability
- Perilunate dislocation or lunate dislocation
- Inflammatory arthropathy (e.g., rheumatoid arthritis)
- Post-traumatic carpal malalignment
Reference: Schmitt R, Lanz U. Diagnostic Imaging of the Hand. TIS. (2008).
Imaging Notes
The capitolunate angle is measured on a true lateral wrist radiograph with the wrist in neutral position. Draw the longitudinal axis of the capitate (through its proximal and distal midpoints) and the longitudinal axis of the lunate (perpendicular to a line connecting its volar and dorsal horns); the angle formed between these two lines is the capitolunate angle. A strict lateral projection is critical — even minor degrees of rotation alter the apparent angle and can lead to a false diagnosis of instability.
When performing the measurement, ensure the pisiform overlies the midportion of the scaphoid on the lateral view as a quality check for true lateral positioning. Digital radiography with angle measurement tools improves reproducibility. If plain radiography is equivocal, MRI or CT arthrography may be used to evaluate the underlying ligamentous structures driving the malalignment.