Abstract: A shaft for a collarless hip joint prosthesis, the shaft having a proximal end formed to support a joint head and a distal end formed to be inserted into a bone channel, the shaft being formed to exhibit a change in the direction of its longitudinal axis in the direction of a selected plane and in a region in the vicinity of its proximal end, and having a rounded cross section presenting a reduced cross-sectional dimension in the direction perpendicular to the selected plane, the shaft having a shoulder located in the region in the vicinity of the proximal end, projecting from the selected plane, and merging in the direction of the longitudinal axis of the shaft into regions having such reduced dimension.