I claim the ornamental design for an elbow guard, as shown and described.
FIG. 1 is a front perspective view of an elbow guard being worn by a baseball player;
FIG. 2 is a top, side perspective view of the elbow guard of FIG. 1;
FIG. 3 is a front view of the elbow guard of FIG. 1;
FIG. 4 is a rear view of the elbow guard of FIG. 1;
FIG. 5 is a left-side view of the elbow guard of FIG. 1;
FIG. 6 is a right-side view of the elbow guard of FIG. 1;
FIG. 7 is a top view of the elbow guard of FIG. 1; and,
FIG. 8 is a bottom view of the elbow guard of FIG. 1.
The dashed lines shown in FIGS. 1 through 8 are included for the purpose of illustrating environmental elements only and form no part of the claimed design.