The ornamental design for a knife handle, as shown and described.
FIG. 1 is a left side perspective view of the knife handle, the right-side being a mirror image, showing my design.
FIG. 2 is a left-side view of the knife handle thereof, the right-side being a mirror image.
FIG. 3 is a top view thereof.
FIG. 4 is a bottom view thereof.
FIG. 5 is an enlarged rear view thereof; and,
FIG. 6 is an enlarged front view thereof.
The broken lines shown in FIGS. 1 through 6 illustrate enviromental structure that form no part of the claimed design. The broken lines shown on the knife handle in FIGS. 1, 2 and 5 illustrate portions of the knife handle that form no part of the claimed design.