Had Surgery On My Knn Sept 30 To Clean Out

had surgery on my knn sept 30 to clean out artirstis then knee started poppin out of joint went back to doctor nov 10 doctor said i need a knee replacement had it replaced on dec 2 the doctor said my knee was full of fluid when he cut it open jump to the second office visit knee was full of fluid again doctor drained off alot went to physical threapy knee has fluid on it again now nocticing knee moving from side to side is this normal