Have A lump below knee cap where joins the tibia diameter of quarter. No pain. Was told about 8 years ago onset of arthritis. Back then the pocket of fluid would burst and then rebuild if pressure applied to it. Now it is firmer. No pain. Notice a little puffy on back side of knee like may be some fluid build up there. No limitation in activity no pain but looks like a deformity and don't know how to get rid of it.