Bruising occurs due to some abnormality in blood or blood vessel..Since bruising in your case has appeared spontaneously without any preceding history of trauma, you need a complete blood count, bleeding time and clotting time estimations..Also the bruising is confined to your dependant part ie lower limbs, which further points that there may be underlying vasculitic component..Ankle swelling is further supporting a rheumatologic component. You don t need to panic for the same but you must get yourself evaluated by either a dermatologist or rheumatologist. I hope you will find this information useful Thanks Take care