As I understand it, "joint" is a British term for roast. Related to pork, a joint could come from the front, middle or back of a hog (boar).
If you could identify the cut of meat, that would be a big help.
If it's a wild boar, I'd guess it's leaner than farm raised animals.
"If you want to make an apple pie from scratch, you must first create the universe." -Carl Sagan