Hi ndistler, I found out what was causing the fluid and swelling. My horse will be turned out this summer, because she can barely walk. What happend was, she acquired a hematoma on her knee associated with an unknown injury, blood pooled into the area, then weeks went by, and scar tissue started forming. A combination of both those things are needing to be worked thru the joint which is painful. I was told by my vet after taking xrays that I need to walk her under saddle 15min, cold hosing it 10 min afer that, and then using a liniment he is supposed to be giving me. That's my summer. Hope your horse is doing ok.