The ornamental design for protective leg pad, as shown and described.
FIG. 1 is a perspective view of the protective leg pad embodying a first embodiment of the new design;
FIG. 2 is a side view thereof;
FIG. 3 is a top view thereof;
FIG. 4 is a bottom view thereof; and,
FIG. 5 is a rear view thereof.
FIGS. 1-5 show features of a protective leg pad in phantom lines. These features are shown for environmental purposes and do not form any part of the claimed design. Further, the phantom lines immediately adjacent the solid-line portions of the design form the boundary of the design, with the phantom lines forming no part of the claimed design.