An external articulation mechanism for pivotably holding the backrest of a vehicle seat on the vehicle. A receiving element can be secured to the vehicle and has a support opening and side walls defining an introduction slot that opens into an open side of the support opening. A pivot member securable to the backrest can be inserted into the support opening via the introduction slot. An arresting mechanism on the receiving element extends over the open side of the support opening and is pivotable between release and arresting positions. A support element disposed on the pivot member has an extension that juts into the introduction slot and that on both sides has deformable projections for resiliently engaging recesses of the side walls of the receiving element.