Provided is a method for designing a patient-specific surgical device for performing knee surgery, which includes determining a first alignment axis and/or a second alignment axis from a knee joint in extension and/or flexion respectively and subsequently designing said surgical device based on the first and/or second alignment axes. Also provided is a method of manufacturing a patient-specific surgical device designed by the aforementioned method. A patient-specific surgical device designed and/or manufactured by the above methods and a method of performing knee surgery with said patient-specific surgical device is further provided.
