Please explain what a puss packet under the patela is have swelling in left leg. knee and leg two sizes bigger than right. have pain in the knee and shin bone. hurts to lift leg and bend leg. also hurts to stand on leg. doctor ordered xray and is sending

Pus : Pus is the thick, goopy material in an infection. It is composed of dead inflammatory cells, called neutrophils, and bacteria. The question is whether you have an infection in your joint, which can be serious and probably needs surgical drainage rather quickly or whether there is another cause of your symptoms. One possibility is a blood clot, which can also be very serious and needs immediate treatment. I hope you are getting care immediately and not waiting for an appointment. The patella is another name for the knee cap. The fact that you had surgery before makes infection a real concern. If you have any hardware, it can get covered with bacteria in a layer called biofilm that is resistant to antibiotics. If you have progressive redness or streaks of red going toward your groin, go to an emergency room rather than waiting. Some infections progress rapidly and can make you deathly ill.