The present disclosure relates to a straight stem (10) for the implantation into a proximal femur the stem (10) comprising a proximal stem section (12) and a distal stem section (14) having a distal end (24), the proximal stem section (12) comprising a connection portion for connecting a neck (16) to the stem (10), the connection portion comprising a collar (18) having, in an anterior-posterior view, a medial contour, the stem (10) having, in an anterior-posterior view, a medial contour and a lateral contour, and the stem (10) having a straight stem center axis (20) between the medial contour and the lateral contour, wherein the medial contour of the stem (10) comprises a concavely curved section extending between a straight medial section (46) and the collar (18), wherein the concavely curved section of the medial contour comprises at least first and second curved sections, the first curved section merging with the straight medial section (46) and the second curved section merging with the medial contour of the collar (18), and wherein the degree of curvature of the first curved section is smaller than the degree of curvature of the second curved section.
