TweetWell I found this small lump behind my left knee about a month ago. I watched it for a few weeks and then decided to go to see my doc about it. My orthopedist sent me in for an MRI of my knee to see what it was, and called this morning to tell me the results. He said it is a baker's cyst from an old injury in my knee that is a result of the tendon repairing itself. He doesn't want me to go under the knife yet unless it gets bigger. Reason I posted in this forum is I was wondering if AAS will cause the cyst to grow bigger. I know there have been several studies out there about AAS increasing the size of certain tumors etc.... Just looking to see if any one has any knowledge about this.