A surgical instrument includes an end effector, a handle assembly, and a knife drive assembly. The end effector includes a first jaw, a second jaw, a knife, and an electrode assembly. The handle assembly includes a housing, and an arm. The arm may pivot the second jaw between the open position and the closed position. The knife drive assembly includes an input assembly, and output assembly coupled with the knife, and a compound pulley assembly. The compound pulley assembly includes a pair of pulley wheels each having an input track, an output track, an input cable, and an output cable. The input assembly can drive the input cable a first proximal distance in order to rotate the pair of pulley wheels in a first angular direction, thereby driving the output cable a first distal direction to actuate the knife from the pre-fired position toward the fired position.
