What Causes Bruising On Ankle After A Knee Injury?

Hello! A week ago I feel on concrete and hit my knee pretty hard. I used ice as soon as I could. After a few days I noticed a bruise in my ankle that would get uglier after I used the leg. I couldn t get an elastic bandage until yesterday due to work but I wrapped my knee and slept with my leg up tonight and when I woke up I noticed the bruise on the ankle was smaller and lighter. I didn t hit my foot when I feel so I m worried.