Tonight I cooked fried chicken on the stove. However, I have seen chicken with brown ligaments or bones, after cooking before. Not just from frying the chicken either. Is it due to the age of the chicken, or an incorrect temperature or overcooking? I hate seeing that when I eat chicken and if I knew what was causing it, I could avoid it, and enjoy my chicken more.
The darkening is harmless. It is more likely to occur in younger birds, since their bones are immature, soft, and porous. It is also exacerbated by deep chilling or freezing, since microscopic ice crystallization will allow various colored substances (e.g., marrow) to coalesce around the bones. When the meat is cooked, these substances will usually turn brown.
Therefore, interior browning can be avoided by using older chickens and avoiding meat that has ever been frozen. Given that most commercial chickens in large countries like the USA are slaughtered very young (less than seven weeks old), it may be difficult, but not impossible, to find an older chicken.
It's likely the brown you are noticing is the blood seeping from the bones during the cooking process, and then turning brown after being exposed to heat.