The present invention relates to alignment device (26) for aligning a block for cutting the posterior (15) femoral condyles (5, 6) during prosthetic knee surgery, a posterior femoral cutting block (29) comprising one or more blade guides (31, 32) and a receiving slot (30) configured to receive a coupling means (24) attached to the alignment device (26), an anterior femoral cutting block (46) disposed with a blade guide (47), said block provided with an attachment means (48', 48", 94, 95) for attaching to the posterior femoral cutting block (29), a distal femoral cutting block (50) disposed with a blade guide (51) provided with an attachment means (52, 55) for joining the block to the posterior femoral cutting block (29), and a kit comprising one or more of the above.