An acetabular implant cup insert for a joint prosthesis, the insert being of the type having a metal shell (1) and a polymer lining (14) lining the inside space (4) of the shell (1), a receptacle (18) for a prosthetic head being formed in the lining (14), the shell presenting on its inside space (4) elements for preventing the lining (14) being extracted from the shell (1) and elements for preventing the lining (14) turning in the shell (1), the insert being characterized in that the elements for preventing the lining being extracted include a stud (11) disposed on the end wall (10) of the shell (1) and presenting at least one groove (12) or lip. An acetabular implant including a cup and an insert of the above type. A joint prosthesis of the type including an acetabular implant of the above type and a prosthetic head.