There have been some health concerns raised (mainly through word of mouth) with regards to the toxicity of chicken haunches.
Apparently, in the industrial breeding and rearing of chickens many harmful chemicals, excessive antibiotics and growth hormones are injected into chickens and the injection is conventionally done at the haunch (also known as the "chicken tip"), hence consumers are warned not to consume the chicken tip.
from some random blog
Chicken tip: also known as "chicken butt", "chicken haunch, refers to the long tail of the parts of the upper end of the chicken butt, juicy meat. This part of the lymph glands concentrated, to be swallowed by macrophages in the lymph glands of bacteria and viruses, and even carcinogens, but can not be broken down, so that the toxins will settle in the haunch. Over time, the chicken tip became large warehouse storage of viruses, bacteria.
How much truth is there to this?
Personally I'm a little sceptical because I find it unlikely industrial breeders inject each chicken individually as opposed to injecting the chemicals into water or feed instead. Also, I have some degree of confidence in food safety authorities.