Hi just looking for any similar stories or advice here. I'm a 22 year old mum of 2 and worried sick about a solid lump behind my knee. First noticed it about 3 weeks ago whilst in the bath, it's on the back of my left knee under the skin to the right it's about the size of a marble and it is solid to touch. It doesn't hurt at all when touched, however it does move around. Everything I've read online is all pointing to cancer and the worry is really affecting my life. Seen my doctor and he had one quick feel and said 'probably just a cyst' which isn't very reassuring as cysts are usually soft to the touch whereas this js rock solid .