The Travellers are a band of Irish people linked by family and often living apart from the larger community. While the various clans of Travellers are traditionally united by blood or marriage, that doesn't mean they all get along, and filmmaker Ian Palmer explores a long-running feud and how it plays itself out in this documentary. The Quinn McDonagh family and the Joyce family are cousins, but they've also been fighting among themselves for generations, long enough that the basis of their anger is no longer clear in anyone's mind. The two families regularly attempt to settle their disagreements through brutal bare-knuckle boxing contests, in which few moves are forbidden and the strongest man wins. For years, than man has been James Quinn McDonagh, a gifted pugilist who can defeat nearly any one, but James has lost interest in fighting and had announced he'll leave the job of defending his family's honor to someone else. That responsibility falls to his younger brother Michael Quinn McDonagh, who wants a chance to prove himself after a humiliating loss to Big Joe Joyce several years before. Big Joe enjoys sending abusive messages to the Quinn McDonagh family, prompting more fights and perpetuating a cycle of violence that seems unlikely to end. Filmed over a period of twelve years, Knuckle was an official selection at the 2011 Sundance Film Festival.