I have had multiple issues with my left knee, meniscus tears post operative, ACL reconstruction, hardware removals due to allergies and a total left knee dislocation. My knee clicks all the time, mild pain from time to time, but I stay active, walk as much as possible. This week I developed bruising on the knee after walking several miles, mild pain but not limiting my day to day. I didn t fall or bump it. Why is it bruised?