i'm sorry to hear you're going through this. it's annoying when our joints don't work correctly! you may be spot on when you say your knee joint feels like it's full of fluid. that could be exactly what's going on. many things can cause the knee joint to temporarily fill up with fluid. as long as you have no signs of a deep vein thrombosis (dvt) such as heat pain and angry redness to the calf area you probably can take a wait-and-see attitude. if the pressure and stiffness in your knee is accompanied by a "lump" on the back of your knee (where the leg bends) you could have a baker's cyst. this type of cyst can be caused by osteoarthritis or an injury. a baker's cyst can be easily diagnosed by mri though some medical professionals can tell simply with a physical examination. these cysts often are easy to feel. since you don't have a fever you can be relatively assured there's no infection process going on. if resting and elevating the knee don't cause the pressure to go away you should consider a visit to your primary care provider for an evaluation. wishing you well!
i have pressure in my right knee but no pain; the pressure limits my ability to bend the knee fully. condition began shortly after i drove for two long days and then played tennis a day later. i am male 45 years old and in generally good health/fitness and healthy weight (5'8" 150lbs). there's no pain unless i try to bend the knee completely. otherwise it's just a sense of pressure like there's a bit of fluid built up inside the knee. my left knee is perfectly fine. i have no other symptoms - no fever for example.