The invention relates to a protection device (1) for a knuckle joint (21) e.g. for the steering and/or suspension of a vehicle, which comprises an annular flange (2) for securing a thermal screen (3) to the knuckle joint, said screen extending lengthwise substantially perpendicular to the flange (2) and widthwise substantially along the annular periphery of the flange. The screen and the flange are formed as a single part in a metal sheet that is folded in a linking area between the screen and the flange, the screen further including a surface portion in the form of a side tab (6) extending along the annular periphery of the flange, said side tab being separated from the flange by a notch (12) in the metal sheet, in the form of a slot.