A prosthesis for restoring a joint between first and second bones (01, 02), the prosthesis comprising: • a first plate; • means for associating this first plate with a resected end of the first bone; • a second plate; • means for associating this second plate with a resected end of the second bone; and • means for mounting the two plates (11, 21) pivotally relative to each other about a pivot axis;the means for mounting the two plates (11, 21) pivotally relative to each other about the pivot axis being constituted by: • a flexible hinge, said flexible hinge comprising: * a plane flexible strip of substantially cylindrical shape; and * two oblong swellings (42, 43) of substantially cylindrical shape, the dimension of the cross-section of each of these two swellings (42, 43) respectively, taken in a direction perpendicular to the plane containing said pivot axis and passing through the two swellings, being greater than the thickness of said flexible strip taken in the same direction; • a hole (44, 45) made in each of the two plates (11, 21), each hole having an end opening out in a first face of the plate in which it is made, the two holes (44, 45) having respective shapes complementary to the two respective swellings (42, 43); • a slot (46, 47) made in each of the two plates (11, 21), the slot made in a plate opening out into the hole made in that plate and into a second one of its faces, and including an end opening out into the first face of the plate; and • the flexible hinge and the two plates (11, 21) being mounted in cooperation in such a manner that the two swellings (42, 43) and the flexible strip are situated respectively in the two holes (44, 45) and in the two slots (46, 47), characterized by the fact that the flexible hinge comprises means for associating these two oblong swellings (42, 43) respectively with two opposite edges of said flexible strip so that the generator lines of the cylindrical shapes of the strip and of the two swellings are substantially parallel to said pivot axis, • a first plate; • means for associating this first plate with a resected end of the first bone; • a second plate; • means for associating this second plate with a resected end of the second bone; and • means for mounting the two plates (11, 21) pivotally relative to each other about a pivot axis;the means for mounting the two plates (11, 21) pivotally relative to each other about the pivot axis being constituted by: • a flexible hinge, said flexible hinge comprising: * a plane flexible strip of substantially cylindrical shape; and * two oblong swellings (42, 43) of substantially cylindrical shape, the dimension of the cross-section of each of these two swellings (42, 43) respectively, taken in a direction perpendicular to the plane containing said pivot axis and passing through the two swellings, being greater than the thickness of said flexible strip taken in the same direction; * a plane flexible strip of substantially cylindrical shape; and * two oblong swellings (42, 43) of substantially cylindrical shape, the dimension of the cross-section of each of these two swellings (42, 43) respectively, taken in a direction perpendicular to the plane containing said pivot axis and passing through the two swellings, being greater than the thickness of said flexible strip taken in the same direction; • a hole (44, 45) made in each of the two plates (11, 21), each hole having an end opening out in a first face of the plate in which it is made, the two holes (44, 45) having respective shapes complementary to the two respective swellings (42, 43); • a slot (46, 47) made in each of the two plates (11, 21), the slot made in a plate opening out into the hole made in that plate and into a second one of its faces, and including an end opening out into the first face of the plate; and • the flexible hinge and the two plates (11, 21) being mounted in cooperation in such a manner that the two swellings (42, 43) and the flexible strip are situated respectively in the two holes (44, 45) and in the two slots (46, 47), characterized by the fact that the flexible hinge comprises means for associating these two oblong swellings (42, 43) respectively with two opposite edges of said flexible strip so that the generator lines of the cylindrical shapes of the strip and of the two swellings are substantially parallel to said pivot axis,