After Four Years Of Right Knee Replacement Grew A Huge

After four years of Right knee replacement grew a huge baker's cyst. For two year aspirated w cortisone shot every 3 months. Five weeks ago had is removed authroscopicly. After 3 week doctored drained blood that looked like jello. After 2 week drained again. Blood not so jelled. I have been sitting in shower and putting warm water and taking my hand and squeezing the lumb then riding the bike for 8 min. I still have a lumb behind my knee and they say it is secondary blood. Will this continue. I already know it will need drained again in two week. Why is this happening? Liz