In posterolateral corner injuries, a tibial external rotation difference of less than 5 degrees corresponds to which grade?

In posterolateral corner injuries, a tibial external rotation difference of less than 5 degrees corresponds to which grade?

• A. Grade 1
• B. Grade 2
• C. Grade 3
• D. Grade 4

Answer: (A)

A small tibial external rotation difference on exam reflects only a mild loss of restraint from the posterolateral corner. The PLC normally limits tibial rotation, especially under load, so when the injury is minor the tibia doesn’t rotate much more than the uninjured side. A difference under 5 degrees therefore corresponds to the mildest grade, Grade 1. As the injury becomes more severe, more structures within the PLC are affected, allowing progressively more external rotation and yielding higher grades. Hence, less than 5 degrees is the best indicator of Grade 1.

A small tibial external rotation difference on exam reflects only a mild loss of restraint from the posterolateral corner. The PLC normally limits tibial rotation, especially under load, so when the injury is minor the tibia doesn’t rotate much more than the uninjured side. A difference under 5 degrees therefore corresponds to the mildest grade, Grade 1. As the injury becomes more severe, more structures within the PLC are affected, allowing progressively more external rotation and yielding higher grades. Hence, less than 5 degrees is the best indicator of Grade 1.