Foot drop after radical nephrectomy surgery?

Peroneal nerve: Isolated foot drop after surgery is likely due to pressure on the lateral aspect of the leg just below the knee during surgery. As seen in the picture, the peroneal nerve is at risk of pressure injury where it crosses the fibula. This kind of "palsy" due to pressure may recover spontaneously over weeks to months. If not, orthotics or surgery to graft a nerve along the injured area may help.

Foot drop: This usually indicates nerve injury during surgery. As the surgery wasn't at the knee area it usually resolves. You don't state when the surgery was done , so feel free to contact your surgeon with this and any related questions.