Suggest Treatment For Swollen And Painful Knee

hi, i have had a very puffy knee for the last year. Mainly on top of the knee cap. It isnt painful and is worse on one side. What is is likely to be caused by and is it likely 2 get worse with age. I'm a 37yr female. I did bang the knee hard approx 8years ago but as i said i have it mildly in the other knee also. I used 2 get dreadful pains in my knees from about 12yrs but have had no pain since it swelled.