I'm 53 and have been on Warfarin for about 10 years due to a DVT in my lower right leg. My clotting issues are completely reverse of yours. I had a knee replacement last June and had to work with the doctors so as not to bleed into the knee joint after surgery. Bleeding into a knee replacement could be as the Doctor described it (Catastrophic) causing infection. About a week prior to surgery or any procedure that involves cutting I have to do what is called bridging. I'll stop the Warfarin until my INR drops below 2.0 and then start with Lovenox injections until the day before the procedure and then hold all anti-coagulants until the day after the procedure and then start with the Lovenox and Wararfin until my INR is back up to 2.0 and then stop the Lovenox. I follow up in the anticoagulation clinic with daily then weekly then monthly blood checks until my INR remains stable between 2.0 and 3.0 (Therapeutic) You’ll likely only be on the Warfarin for a couple of weeks and it’s not likely in my experience to cause you any problems. It is the main ingredient in Rat poison but at much higher levels per weight ratio than you’ll be taking. Warfarin takes about three or four days of taking it to get you to a therapeutic level thereby preventing blood clots. Lovenox injections are very expensive at $100.00 a pop. When I'm using them I have to take them twice a day for about two weeks. It works out to about $3000.00 per procedure. Another big point is keeping your diet the same. A big increase/decrease in eating greens can/will change your INR. A big increase in greens from your normal diet will cause your INR to drop and other things like cranberries can cause your INR to spike. Make sure that you talk with your Doctor about any and all meds/vitamins/supplements that you’re taking or plan to start taking because they can also react with the Warfarin. Good luck with the new knee.