I am a 51 year old female who has been going to the gym 3 times a week (an hour each time) for the last five weeks after years of no exercise at all. Last night I discovered a large, painless lump at the back of my leg about 2 inches above the bend in my knee. It doesn't move or hurt when touched and it isn't red or discoloured in any way. Could it be linked to the exercise?