A kit for use in performing hip joint arthroplasty, the kit comprising: a trial for use in performing joint arthroplasty, the trial to be fitted to a cavity in the canal of a long bone and to assist in performing a trial reduction in performing joint arthroplasty, the trial including a stem portion which defines a longitudinal axis and a neck portion connected to the stem portion, the stem portion and the neck portion each having a keyed feature (146, 148), an implant for use in performing joint arthroplasty, the implant to be fitted to a cavity in the canal of a long bone and to assist in performing joint arthroplasty, the implant including a stem portion and a proximal body portion connected to the stem portion, and an instrument for observing or replicating the relative angular orientation of the stem and neck portions of the trial, which includes a body and a member which can link the instrument to the trial, characterised in that the neck portion of the trial can be selectively operably connected to the stem portion of the trial in a plurality of selectable rotational positions with respect to the axis which is defined by the stem portion of the trial, and the proximal body portion of the implant can be selectively operably connected to the stem portion of the implant in a plurality of selectable positions with respect to the stem portion of the implant, and the instrument includes (a) a body, (b) a first member mounted on the body for cooperation with the stem portion of the trial and which has a keyed feature for cooperating with the keyed feature on the stem portion of the trial to as to link the first member angularly to the stem portion of the trial, (c) a second member mounted on the body for cooperation with the neck portion of the trial and which has a keyed feature for cooperating with the keyed feature on the neck portion of the trial to as to link the second member angularly to the neck portion of the trial, the first member being movable rotationally relative to the body so that the first and second members can engage the stem and neck portions respectively of the trial, and the instrument including indicia providing a measuring scale to indicate the relative angular position of the first member relative to the second member. a trial for use in performing joint arthroplasty, the trial to be fitted to a cavity in the canal of a long bone and to assist in performing a trial reduction in performing joint arthroplasty, the trial including a stem portion which defines a longitudinal axis and a neck portion connected to the stem portion, the stem portion and the neck portion each having a keyed feature (146, 148), an implant for use in performing joint arthroplasty, the implant to be fitted to a cavity in the canal of a long bone and to assist in performing joint arthroplasty, the implant including a stem portion and a proximal body portion connected to the stem portion, and an instrument for observing or replicating the relative angular orientation of the stem and neck portions of the trial, which includes a body and a member which can link the instrument to the trial, characterised in that the neck portion of the trial can be selectively operably connected to the stem portion of the trial in a plurality of selectable rotational positions with respect to the axis which is defined by the stem portion of the trial, and the proximal body portion of the implant can be selectively operably connected to the stem portion of the implant in a plurality of selectable positions with respect to the stem portion of the implant, and the instrument includes (a) a body, (b) a first member mounted on the body for cooperation with the stem portion of the trial and which has a keyed feature for cooperating with the keyed feature on the stem portion of the trial to as to link the first member angularly to the stem portion of the trial, (c) a second member mounted on the body for cooperation with the neck portion of the trial and which has a keyed feature for cooperating with the keyed feature on the neck portion of the trial to as to link the second member angularly to the neck portion of the trial, the first member being movable rotationally relative to the body so that the first and second members can engage the stem and neck portions respectively of the trial, and the instrument including indicia providing a measuring scale to indicate the relative angular position of the first member relative to the second member.