Abstract: A hinge joint assembly including a first body having a first circular serrated edge located around a first central axis; a second body having a second circular serrated edge located around a second central axis, said second circular serrated edge corresponding with and adapted to engage with the first circular serrated edge; an axle rod, extending through the first central axis and the second central axis, adapted to enable the first and second bodies to rotate relative to one another; biasing means, positioned between the first body and the second body, for biasing said first and second bodies away from each other along the axle rod; movement limiting means for preventing the second body from being separated from the first body beyond a pre-determined distance; and a cam element, rotatable about the axle rod, adapted to move the second body relative to the first body, from a joint locked position to a joint unlocked position.