I claim the ornamental design for an ankle support, as shown and described.
FIG. 1 is a perspective (front, top, right) view of my new design in an ankle support, as it would appear applied to the ankle and adjacent areas of the leg and foot of a person;
FIG. 2 is a front elevation view of my new design in the ankle support of FIG. 1;
FIG. 3 is a left elevation view of my new design in the ankle support of FIG. 1;
FIG. 4 is a back elevation view of my new design in the ankle support of FIG. 1; and,
FIG. 5 is a right elevation view of my new design in the ankle support of FIG. 1.
The parts shown by means of broken lines in the drawings are not part of the claimed design. The top elevation view and the bottom elevation view have been omitted because the surfaces of the top and bottom of the product bear no ornamentation.