MRI-based assessment of posterior condylar cartilage defects and their impact on femoral component rotational alignment in osteoarthritic knees

Rotational axes vary with KOA severity and coronal alignment on MRI, and these phenotype-dependent differences explain why a uniform PCA + 3° approach produced a high malrotation rate (internal in many valgus KOA knees and excessive external in many varus KOA knees). Therefore, femoral rotational alignment planning should be individualized using anatomy-based references-prioritizing the SEA, cross-checking with TAL-SEA, and applying directional tolerances that avoid internal rotation relative to the SEA-rather than relying on a fixed-angle rule.