I teach nikyo as turning the kote using uke's hand as a handle. Like turning a socket using the handle of the socket wrench.
Initially, I teach them to tuck it in nice and firm (since we're in hanmi, they tuck it into the front shoulder) then turn the kote by bending at the waist and bending the front knee. The "foundation" of the technique is the back foot.
Later, however, I show my students how, when nage can maneuver uke's elbow below his kote, they can increase the effectiveness of the technique by adding hip-turning to the equation. To do this, one has to bend both knees during the turn.
Any of the Pikes Peak folks here that trained with me? They can tell you about what that nikyo is like....