An incision is a surgical cut.
Surgical approaches to the knee
The decision as to where to do the skin incision for any particular knee surgery is referred to as the 'surgical approach'. The same term also encompasses how and where the underlying tissues are moved aside in order to access the deeper structures. If the procedure is an arthroscopy rather than an open operation then the incisions are tiny and are called 'portals'.
Surgical approaches for total knee arthroplasty. Vaishya R, Vijay V, Demesugh DM and Agarwal AK. J Clin Orthop Trauma. 2016 Apr-Jun; 7(2): 71–79.
Posterior Surgical Approach to the Knee. Faucett SC, Gannon J, Chahla J, Ferrari MB and LaPrade RF. Arthrosc Tech. 2017 Apr; 6(2): e391–e395.