This disclosure relates to surgical instruments for alignment of bone cuts during surgeries on joints and in particular, during total replacement of joints. The surgical instrument comprises a contact surface shaped to fit a prepared end of the first bone of the joint and an artificial articular surface that imitates the native articular surface of the first bone that has been removed by the preparation of the first bone. The artificial articular surface is pivotable in relation to the surgical instrument. The instrument can be fitted onto the prepared bone and coronal balancing can be performed. After fixing a further instrument to the second bone the joint can be balanced in flexion. At the optimal flexion angle, the slope and the cutting depth can be adjusted to achieve alignment. The further instrument is then used as a guide for cutting the second bone at the resulting cutting depth, slope and varus/valgus angle.