Localizing peroneal nerve lesions to the knee by motor conduction studies.

We studied peroneal motor conduction in 186 normal patients (206 nerves) and in 36 patients with 38 peroneal nerve lesions localized to the knee by electromyography. The efficiency of the test, or percentage of times the test results were true, was used to find the optimal point to separate the normal patients from patients with peroneal nerve lesions at the knee. This analysis revealed that the best indicator for localizing a peroneal nerve lesion to the knee was a greater than 20% drop in peroneal motor amplitude across the knee. This gave a calculated efficiency of 99.52% and detected 60% to 70% of peroneal nerve lesions at the knee.