Hi Dr Rynne, I m a professional athlete who has been suffering from patella tendinopathy and my doctors are planning on injecting my knee with a cortisone injection to ease the tender pain I m experiencing in the tissue that lays underneath the tendon. As you know cortisone is a steroid and is a prohibited substance in many sports, I d like to know how long it takes for the drug to leave my body completely, so that it won t appear in a doping test if I were to take one.