An articulated prosthesis for a tricuspid or a mitral valve, comprising: a distal annular portion, a central annular portion and a proximal annular portion (8, 9); a first plurality of rigid arms hinged to an outer side surface of said distal annular portion; a second plurality of rigid arms hinged to an outer side surface of said proximal annular portion (8, 9); a third plurality of rigid arms each of which is hinged to an outer side surface of said central annular portion, from one end; a fourth plurality of rigid arms each of which is hinged to an outer side surface of said central annular portion, from one end, and to a corresponding end of a rigid arm of said second plurality, from an opposite end; rigid arms of said third plurality and/or of said fourth plurality having facing catching surfaces, the catching surfaces of the rigid arms of said third plurality defining also pointed projections configured for spiking leaflets of a tricuspid or mitral valve; the articulated prosthesis being movable from a distended configuration, in which all said rigid arms (10, 11, 12, 13) hinged in correspondence of their ends are distended, to an expanded configuration, in which said proximal annular portion (8, 9) is threaded throughout said central annular portion and is engaged with said distal annular portion, the rigid arms of said third plurality and fourth plurality being configured to hold therebetween leaflets of a tricuspid or mitral valve, with said pointed projections spiking the leaflets, when the articulated prosthesis is in the expanded configuration; characterized in that each rigid arm of said third plurality of rigid arms is hinged to a corresponding end of a rigid arm of said first plurality, from an opposite end; said rigid arms of said third plurality and/or of said fourth plurality having respective knurling defined on the facing catching surfaces; said distal annular portion having an internal screw thread, said proximal annular portion (8, 9) having: - a cylindrical collar on a side surface of which said second plurality of rigid arms is hinged, and - a screw engaged into said collar and supported thereby so as to be free to rotate along a longitudinal axis of the screw, the screw being configured to engage with said internal screw thread, said central annular portion defining a through hole for letting said screw pass through. a distal annular portion, a central annular portion and a proximal annular portion (8, 9); a first plurality of rigid arms hinged to an outer side surface of said distal annular portion; a second plurality of rigid arms hinged to an outer side surface of said proximal annular portion (8, 9); a third plurality of rigid arms each of which is hinged to an outer side surface of said central annular portion, from one end; a fourth plurality of rigid arms each of which is hinged to an outer side surface of said central annular portion, from one end, and to a corresponding end of a rigid arm of said second plurality, from an opposite end; rigid arms of said third plurality and/or of said fourth plurality having facing catching surfaces, the catching surfaces of the rigid arms of said third plurality defining also pointed projections configured for spiking leaflets of a tricuspid or mitral valve; the articulated prosthesis being movable from a distended configuration, in which all said rigid arms (10, 11, 12, 13) hinged in correspondence of their ends are distended, to an expanded configuration, in which said proximal annular portion (8, 9) is threaded throughout said central annular portion and is engaged with said distal annular portion, the rigid arms of said third plurality and fourth plurality being configured to hold therebetween leaflets of a tricuspid or mitral valve, with said pointed projections spiking the leaflets, when the articulated prosthesis is in the expanded configuration; characterized in that each rigid arm of said third plurality of rigid arms is hinged to a corresponding end of a rigid arm of said first plurality, from an opposite end; said rigid arms of said third plurality and/or of said fourth plurality having respective knurling defined on the facing catching surfaces; said distal annular portion having an internal screw thread, said proximal annular portion (8, 9) having: - a cylindrical collar on a side surface of which said second plurality of rigid arms is hinged, and - a screw engaged into said collar and supported thereby so as to be free to rotate along a longitudinal axis of the screw, the screw being configured to engage with said internal screw thread, - a cylindrical collar on a side surface of which said second plurality of rigid arms is hinged, and - a screw engaged into said collar and supported thereby so as to be free to rotate along a longitudinal axis of the screw, the screw being configured to engage with said internal screw thread, said central annular portion defining a through hole for letting said screw pass through.