it could be the vitamin k issue but this is something that i have happen from time to time, usually about once a year when i'm stressed out or getting sick. the dr told me that it was erythema nodosum. bascially what i get is my ankles or foot, and occasionally on up the leg will swell and be sore, i've had it before and everyone who saw it swore i had broken my ankle and while it was swollen it felt like it, it had turned all purple and stuff.