The ornamental design for a knife handle, as shown and described.
FIG. 1 is a perspective view of the knife handle showing my new design;
FIG. 2 is side view thereof, the opposite side being a mirror image thereof;
FIG. 3 is a front view thereof, the rear view being a mirror image thereof;
FIG. 4 is a top view thereof;
FIG. 5 is a bottom view thereof; and,
FIG. 6 is an enlarged partial view of the texture of the knife handle according to my new design.
The broken lines are for illustrative purposes only and form no part of the claimed design. It is understood that the texture shown is contiguous throughout the handle.