Normal Anterior Drawer Sign Size on Radiography
The anterior drawer sign refers to the anterior displacement of the talus relative to the tibia when an anterior stress force is applied to the ankle, assessed on lateral stress radiography. It serves as a key indicator of anterior talofibular ligament (ATFL) integrity and is routinely used to evaluate chronic lateral ankle instability. Accurate measurement guides clinical decision-making regarding conservative versus surgical management.
Normal Reference Values
| Orientation | Measurement |
|---|---|
| Lateral | >10 mm |
Clinical Significance
On lateral stress radiography, anterior talar translation exceeding 10 mm is considered abnormal and indicates significant laxity of the ATFL, the primary restraint to anterior talar displacement. Values at or below this threshold are generally within normal limits, though side-to-side comparison (>3 mm asymmetry) may add diagnostic value in equivocal cases.
An abnormal anterior drawer sign most commonly reflects ATFL rupture or chronic lateral ligamentous insufficiency. Pitfalls include patient guarding limiting adequate stress application, variations in foot positioning, and concurrent calcaneofibular ligament (CFL) injury that can amplify displacement. Clinical correlation with physical examination findings remains essential.
- Acute ATFL rupture following inversion injury
- Chronic lateral ankle instability (mechanical)
- Combined ATFL and CFL ligamentous disruption
- Generalized ligamentous laxity (false positive)
- Post-surgical or post-immobilization residual laxity
Reference: DiGiovanni CW, M.d. JG. Foot and Ankle, Core Knowledge in Orthopaedics. C.V. Mosby. (2007).
Imaging Notes
On lateral stress radiography, the anterior drawer test is performed with the patient seated, the knee flexed to 90°, and the foot in slight plantarflexion. The examiner applies a firm anterior force to the heel while stabilizing the distal tibia. The radiograph is taken in the true lateral projection, and displacement is measured as the distance from the posterior articular surface of the tibia to the corresponding point on the talar dome. Ensuring a true lateral without rotation is critical to avoid measurement error.
Fluoroscopy-assisted stress views improve reproducibility and allow real-time assessment. Bilateral comparative views are recommended when unilateral laxity is uncertain, as absolute values alone may be insufficient in hypermobile individuals. Adequate patient relaxation, occasionally aided by local anesthesia, is necessary for reliable stress application.