Anatomical Landmarks Required for TKA

The rotational position of the femoral component has implications for patellar tracking, medial and lateral ligament balance in knee flexion, rotational alignment against the tibial component, and foot orientation in extension. Therefore, determining the correct rotational position of the implant is necessary. Figure 17.1 illustrates commonly used anatomical landmarks for determining femoral rotation are. Patellar tracking deteriorates when the femur is internally rotated beyond the posterior condylar axis (PCA) [1]. However, the medial gap in the flexion position loosens when the femur is externally rotated beyond the clinical epicondylar axis (CEA). In addition, excessive external rotation of the femoral component results in external rotation of the lower leg and foot during knee extension. Conversely, excessive internal rotation results in internal rotation of the lower legs and feet. Before cementing the implants, it is essential to check foot orientation and rotational discrepancies between the femoral components and tibial inserts. The CEA or PCA is rotated externally or internally by approximately 3° relative to the surgical epicondylar axis (SEA) [2–5]. When using mechanical alignment in TKA and positioning the femoral component rotationally between the CEA and PCA, it appears not to cause any major clinical problems mentioned above.