I have brown frecklish spots on both my sides of my ankles. It looks like it is spreading up my legs. What could cause this?

Discolored ankles. It is common when there is vein dysfunction for staining of the skin to occur. This is caused by leakage of hemosiderin from pressure within the veins.
Vascular. Very often small vessels leak and the skin becomes discolored. Support stockings may help.
Definitely a skin . Issue that one of our expert dermatiologists will be able to help you with! best of luck!