A prosthesis comprises having two portions independent of each other, a first portion and a second portion, at least one of which includes an articular surface, said first portion and said second portion each comprising a circular seat delimited by an arched wall. An element of the prosthesis is an O-ring in an elastically deformable material, and one of said seats is dimensioned to receive a radially outer portion of this ring while the other seat is dimensioned to receive a radially inner portion of this ring.
