A prosthetic trial for a j oint prosthesis includes a first piece (12) having a proximal section and a distal section for implantation in a bone. A second piece (14) includes a recess (38) receiving at least the proximal section of the first piece. A locking mechanism is at least partially disposed within the second piece. The locking mechanism is biassed into a locking position in which the mechanism locks the first piece within the recess of the second piece. The locking mechanism is accessible outside said body to be pulled into a releasing position to unlock the first piece from the second piece.
