It should depend upon the cause of the fluid accumulation in the knees. If it is inflammatory in nature (like in rheumatoid arthritis) then, unless treated with modern scientific medicines, is likely to recur and then slowly destroy the joint. On the other hand if it is due to injury etc. it would get absorbed naturally and usually would not recur. In non-inflammatory-degenerative arthritis like osteoarthritis it may recur with each new crack in the cartilage and further damage the joint. This would require change in life-style, weight reduction and appropriate physiotherapy.