INTRODUCTION: Direct nerve repairs fare better than grafted nerves, especially for large caliber nerves. Numerous surgical techniques are used to achieve tension-free end-to-end repairs for large gaps in the sciatic nerve (SN) and common peroneal nerve (CPN), including distal nerve mobilization, transposition, side-branch neurectomy, or even shortening of the femur with distraction osteogenesis. However, leg flexion with serial distraction is the simplest, least morbid, and most easily implemented technique. METHODS: Eight fresh cadavers with pelvis intact were dissected to determine the relationship between degrees of knee flexion (ranged from 0 to 90-degree flexion) and the gap length overcome with nerve excursion. Additional excursion from SN side-branch neurectomy was also assessed. RESULTS: We found an approximately linear relationship between knee flexion and nerve excursion. In the mid-thigh there was 7-9 mm of SN excursion per 10 degrees of flexion, and 10-11 mm of SN excursion per 10 degrees of flexion with neurectomy. There was 11-13 mm of CPN excursion per 10 degrees of flexion in the distal half of the thigh. CONCLUSIONS: Knee flexion can significantly augment the ability to achieve an end-to-end repair of the SN and CPN. Simplified, each 10 degrees of knee flexion provides about 1 cm of additional length for both nerves, which is essentially constant throughout the arc of flexion. Neurectomy allows approximately 1-2 cm in total additional length at full flexion in fresh cadavers. Approximately 10 cm total excursion can be gained at 90-degree knee flexion with side-branch neurectomies. We recommend 45-90 days of progressive extension to respect the safe regeneration timing of 1-2 mm/day from a repair performed with 90-degree knee flexion.