1 Large numbers of red blood cells may be caused by bleeding in the joint from injury, inflammation, or abnormal clotting of the blood. 2  Large numbers of white blood cells may be caused by gout, pseudogout, other types of arthritis (such as rheumatoid arthritis), psoriatic arthritis, injury, or infection.nfection, bleeding, or damage to the tendon, nerve, or joint is rare. Sometimes your doctor may not be able to draw any fluid out. The joint space may be too small, you may have scar tissue in the joint space, or there may not be any fluid in the joint. The joint may be sore for 1 to 2 days after the procedure.