It's not the first time I've found them, but after picking dozens of them out of some shanks I was browning, I finally tossed them. I've only ever found them in deer shanks. How about yourself?
I'm not sure how to exactly put it into words but they were kind of wove around in a nickle size area just under that membrane outside the meat that's somewhat see through and between the layers of the shank. Not actually in the meat.