A dial test performed at 30 degrees of knee flexion is most consistent with injury to which structure?

• A. PCL
• B. PLRI
• C. IT Band
• D. Meniscal Lesion

Answer: (A)

The dial test uses external rotation of the tibia at two knee flexion angles to tell apart injuries of the PCL versus the posterolateral corner. At 30 degrees of knee flexion, the PCL is the main restraint to tibial rotation. If the PCL is torn, the tibia can rotate externally more than on the uninjured side, so you see a noticeable increase in external rotation. That pattern points to a PCL injury.

Injury to the posterolateral corner tends to show up with the knee flexed more (around 90 degrees) rather than at the shallow 30-degree angle. The IT band and meniscal lesions don’t typically produce a characteristic change in external rotation on this test, so they aren’t the best explanations for a 30-degree dial test finding.

So, a dial test performed at 30 degrees of knee flexion best aligns with PCL injury because the PCL’s restraint to external rotation is most evident at that angle, and loss of that restraint results in increased external rotation on the affected side.