What X-ray view is recommended for assessing patellar tracking, and can Valium (diazepam) be used for management?

X-ray Views for Patellar Tracking Assessment

For assessing patellar tracking, a tangential axial radiographic view (such as the Merchant view) is the recommended imaging modality, while Valium (diazepam) is not indicated for management of patellar tracking disorders.

Optimal X-ray Views for Patellar Tracking

• The standard radiographic examination for evaluating patellar tracking should include a tangential axial view of the patellofemoral joint, which demonstrates the degree of patellar tilt or subluxation 1
• Weight-bearing axial radiographs are recommended to better assess patellofemoral kinematics, as they more accurately represent in vivo conditions 1, 2
• A complete knee examination should include anteroposterior (AP), lateral, and tangential axial views of the patellofemoral joint 1
• The lateral view should be obtained with the knee at 25-30 degrees of flexion to demonstrate the patella in profile 1

Diagnostic Value of Different Views

• Axial views at 30 degrees of knee flexion are traditional for evaluating patellar tracking, but have shown only 62% sensitivity for detecting patellar dislocation 3
• Standing lateral views at 0 degrees (full extension) have demonstrated 98% sensitivity for detecting prior patellar dislocation, making them valuable in the diagnostic workup 3
• The combination of axial and lateral flexed views provides high specificity (93%) for confirming patellofemoral malalignment 3
• Weight-bearing axial views with the patient in semi-squatting position (45 degrees knee flexion) show significant differences in patellar position compared to standard unloaded Merchant views, and correlate better with clinical symptoms 2

Advanced Imaging for Patellar Tracking

• When standard radiographs are insufficient, CT is the modality most commonly used for measuring axial malrotation and component rotation that may affect patellar alignment 1
• Motion-triggered cine MRI during active knee extension can reveal statistically significant differences in patellar tracking patterns between patients with maltracking and healthy subjects that may not be apparent on static images 4
• Dynamic imaging studies are important for diagnosis of patellofemoral maltracking, as passive knee extension may not reproduce the abnormal tracking seen during active motion 4

Pitfalls and Considerations

• Patellofemoral instability can occur from imbalance in the extensor mechanism, excessive tightness of the lateral retinaculum, or valgus alignment 1
• Minor differences in positioning can greatly alter the appearance of periprosthetic lucencies, so fluoroscopically positioned images may provide improved visualization in post-surgical cases 1
• There is no evidence supporting the use of Valium (diazepam) for management of patellar tracking disorders in the provided guidelines 1, 5
• Patellar tracking measurement is significantly affected by basic definitions of coordinate systems, reference points, muscle loading, and tibial rotation, making standardized assessment challenging 6

Recommended Radiographic Parameters

• For patellofemoral evaluation, three key measurements are recommended: patellofemoral angle, patellofemoral index, and patellofemoral displacement 7
• The patella typically translates medially in early knee flexion and then laterally as flexion increases, making dynamic assessment valuable 6
• Interpretation of varus and valgus alignment is improved on AP views obtained in 10 degrees of internal rotation compared with neutral AP views 1