Normal Lunotriquetral Angle Size on Radiography
The lunotriquetral angle describes the angular relationship between the lunate and triquetrum on lateral wrist radiographs, reflecting the integrity of the lunotriquetral ligament complex. Accurate measurement of this angle is essential for identifying carpal instability patterns, particularly volar intercalated segment instability (VISI). Deviations from the normal value can indicate significant ligamentous disruption that may require surgical intervention.
Normal Reference Values
| Orientation | Measurement |
|---|---|
| Lateral | 14¡ |
Clinical Significance
The established normal lunotriquetral angle is 14° on the lateral projection. Disruption of the lunotriquetral ligament allows the triquetrum to flex relative to the lunate, altering this angle and producing a VISI deformity pattern. VISI is characterized by palmar flexion of the entire proximal carpal row and is the classic consequence of lunotriquetral instability.
Clinicians should correlate radiographic angle measurements with clinical findings such as ulnar-sided wrist pain, a positive lunotriquetral ballottement test, and MRI or arthroscopic findings. Isolated lunotriquetral ligament tears can be subtle, and static radiographs may appear near-normal in partial tears; stress or dynamic views improve sensitivity.
- Lunotriquetral ligament tear (partial or complete)
- VISI pattern carpal instability
- Ulnar impaction syndrome with secondary ligamentous attenuation
- Post-traumatic carpal malalignment
- Inflammatory arthropathy with ligamentous laxity
Reference: Doyle JR. Hand And Wrist. Philadelphia: Lippincott Williams & Wilkins, c2006. (2006).
Imaging Notes
Measurement is performed on a true lateral radiograph of the wrist obtained in neutral position, with the forearm in neutral rotation and the wrist neither flexed nor extended. The lunotriquetral angle is formed by the intersection of the longitudinal axis of the lunate and the longitudinal axis of the triquetrum. Strict lateral positioning is critical; even minor obliquity introduces significant measurement error and can falsely suggest malalignment.
When static lateral views are equivocal, dynamic stress views in radial and ulnar deviation or clenched-fist projections may unmask occult instability. Comparison with the contralateral wrist is helpful given physiologic variability. MRI with dedicated wrist coil or MR arthrography is recommended for definitive ligament assessment when radiographic findings are inconclusive.