I am exactly 4 weeks and 1 day post-op. My recovery has been going well. I feel that I'm active and strong, yet not at 100%, of course. I recently went on a trip with my family which included swimming and a short and manageable hike. The back of my knee now has a NEW black bruise beginning behind my knee on the inside portion of my leg. I was warned that when I began to run again that my hamstring would begin to "scream" at me and I would think that I re-injured myself. Is the bruising my "hamstring" screaming or is this a normal part of the process? And, just curious what causes new bruising?