A Muay Thai enthusiast, Knox stripped down to show off his battle-ready physique, looking every inch the spitting image of his father's iconic character Tyler Durden from the 1999 film.
The American, 38, rose to international prominence throughout a series of highly publicised trials in which she was twice convicted and acquitted for the murder of her Meredith Kercher in 2007.
Ms Knox, 38, was convicted of murdering British student Meredith Kercher, 21, in Perugia, Italy, in November 2007 before her conviction was overturned and she was released in 2011.
Ms Knox, 38, was convicted of murdering British student Meredith Kercher, 21, in Perugia, Italy, in November 2007 before her conviction was overturned and she was released in 2011.
Knox, 38, was twice convicted and twice acquitted of Ms Kercher's murder in Perugia, Italy - after she died while the pair lived together studying abroad in November 2007.