and lateral surfaces 901 of the femoral implant 905 the illustrated cross sections being shown at even increments of approximately 10 mm measured from the proximal end fig1 a to the distal end fig1 i respectively in some embodiments as schematically illustrated the ratio of medial 902 surface dimension to lateral 901 surface dimension at a particular transverse cross section of the stem changes from a first e g proximal or distal portion e g fig1 a of the stem to a second e g proximal or distal portion e g fig1 i of the stem in some embodiments the ratio of medial 902 surface dimension to lateral 901 surface dimension e g fig1 a is greater than 1 1 such as greater than 1 1 1 1 2 1 1 3 1 1 4 1 1 5 1 1 75 1 2 1 2 5 1 3 1 4 1 5 1 6 1 7 1 8 1 9 1 10 1 or more while the ratio of medial 902 surface dimension to lateral 901 surface dimension e g fig1 i is less than 1 1 such as less than 0 9 1 0 8 1 0 7 1 0 6 1 0 5 1 0 4 1 0 3 1 0 2 1 or less in some embodiments the ratio of medial 902 surface dimension to lateral 901 surface dimension changes e g increases or decreases by at least about 5 10 15 20 25 30 35 40 45 50 60 70 75 80 90 100 150 200 250 300 350 400 450 500 600 700 800 900 1000 or more or increases by at least 2 u00d7 3 u00d7.