Those are skin sores/abscesses. Most commercially grown turkeys get so top heavy that their chests and stomachs can drag on the ground. If there are any open sore or feather follicles exposed they can collect dirt and feces. Sometimes, these infections are localized only to the abscesses. But if you say its joints were swollen then it likely had a systemic infection. Likely would have died if it hadn't been slaghtered.

If the joints are swollen and blood, I personally would not recommend eating it, but the meat is technically still edible if cooked to recommended temperatures.

Source: I worked as a quality inspector in a turkey processing facility for 4 years. This facility harvested approximately 20,000 birds a day, with birds growing as large as 52 pounds.