In 1997, I had a DVT. Suddenly, I couldn't bend my knee. It was hilarious, until the doctor whisked me off to hospital and they injected something in my belly to de-clot me.
What had happened, was the blood in the main vein in my left leg, had clotted. And my heart was pumping the blood down, but it couldn't get back up. The big danger is that part of the clot could break off, and be washed though to the lung, and you can see how that isn't going to end well.
Blood is supposed to clot, on contact with air. That's why, when you cut yourself, you soon stop bleeding. Also, you can have internal damage (a bruise) and there's also a stop-bleeding mechanism there. If you're lacking that mechanism, then you're haemophiliac, and that's *very* bad news.
Anyway. I was out of hospital the next day, but it took a few weeks for the swelling in my foot to go down. And they tested my blood, and I have Leyden Factor 2 and Leyden Factor 5.
Leyden Factor 5 isn't rare, about 5% of Caucasians have it. But 30% who get a DVT have it, and these days, they normally test anyone who has a DVT. It's hereditary. If you have it, your blood is more likely to clot. I guess this is a good thing if you're active and under 35, because it means you're less likely to die of blood loss if you get a serious wound, and we're evolved to last maybe 35 years.
Leyden Factor 2 is less common, about 2% of Caucasians have it.
So the doctor prescribed Warfarin, used as A) rat poison and B) as an anti-coagulant. I take Warfarin each day, and it makes my blood thinner. So I'd better not have any bad wounds. If I get a scratch or small cut, it seems to heal the same as it did before I went on Warfarin, but if I have any sort of surgery, I have to go off it for a few days beforehand. No big deal.
Then, a few years later, I saw a doctor about something else entirely, and he was surprised that I wasn't wearing compression socks. That was because no-one had said I should. He explained that one effect of the DVT, would have been to mess up the valves in my veins.
There's a long distance between your foot and your heart, and that would mean that there's four more feet of blood pressure down at your toes than the rest of you. But the design of your veins has an answer for that - there's valves in the vein, and they relieve the pressure. But the DVT has damaged those valves. Down around my ankle, there's a spot that's a bit red; that's the blood pressure down there causing that.
Compression socks are advised after a DVT. So I started wearing them on the leg that had it. It's impossible for me to tell if it does any good, but it doesn't cause any problems. I have to buy new ones every so often; they wear out pretty fast. And so today I went on Ebay and ordered a bunch more, which should last me another few years.