A retentive and removable trial bearing insert is used with a total hip replacement joint. The joint includes a dual mobility or bipolar prosthetic cup which has a part-spherical bearing insert with a part-spherical inner bearing surface which engages a part-spherical bearing head on a femoral stem. The bearing comprises a part-spherical trial inner bearing element dimensioned to replace the part-spherical bearing insert and which includes releasable retaining element which engages the bearing head of the femoral stem or a trial bearing head thereof to hold the trial bearing element in place thereon.
