A hinge joint wherein one of the leaves is secured to a fixed part and the other leaf is secured to the pivotable back rest of a seat in motor vehicle and is pivotable with reference to the fixed leaf about the axis of a pintle which can be rotated by a hand wheel or a motor. The other leaf carries a braking member with a cylindrical or frustoconical internal surface which is engaged by the peripheral surface of a prestressed elastic split ring defining a gap for the projection of a blocking element which is affixed to the pintle and urges the split ring into stronger frictional engagement with the braking member when the back rest is acted upon to pivot the other leaf. A coupling device is secured to the hand wheel or to the motor to disengage the split ring from the braking member when the pintle is rotated by the hand wheel or by the motor. The end portions of the split ring flank the projection of the blocking element and are flanked by two protuberances of the coupling device.