This 1993 cadaveric study of 75 femurs establishes the surgical epicondylar axis as a reproducible secondary landmark for femoral component rotation in TKA. It quantifies the posterior condylar angle — the offset between the posterior condylar line and the surgical epicondylar axis — and demonstrates that this angle differs significantly by sex. The goal: give surgeons a reliable rotational reference when posterior condyles are damaged, worn, or already resected.
Femoral rotational alignment is one of the most consequential decisions in TKA — malrotation drives patellofemoral complications including subluxation, eccentric wear, and anterior knee pain. The posterior condyles are the default reference in primary TKA, but they are nearly always unusable in revision cases, where prior cuts and component removal distort the anatomy.
This paper gives you a concrete decision rule: when posterior condyles cannot be used, identify the surgical epicondylar axis (lateral prominence to medial sulcus) and dial in 3.5° of external rotation for males and essentially 0° for females relative to that axis.
Do not apply a generic "3 degrees external rotation" rule to everyone. Female anatomy sits nearly parallel to the surgical epicondylar axis, and over-rotating a female femoral component is a real intraoperative error this paper prevents.
This work became the anatomic foundation for epicondylar-axis-based referencing in computer navigation and patient-specific instrumentation. You will see this axis called out explicitly in modern TKA systems.
Determining the Rotational Alignment of the Femoral Component in Total Knee Arthroplasty Using the Epicondylar Axis.
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This 1993 cadaveric study of 75 femurs establishes the surgical epicondylar axis as a reproducible secondary landmark for femoral component rotation in TKA. It quantifies the posterior condylar angle — the offset between the posterior condylar line and the surgical epicondylar axis — and demonstrates that this angle differs significantly by sex. The goal: give surgeons a reliable rotational reference when posterior condyles are damaged, worn, or already resected.
Femoral rotational alignment is one of the most consequential decisions in TKA — malrotation drives patellofemoral complications including subluxation, eccentric wear, and anterior knee pain. The posterior condyles are the default reference in primary TKA, but they are nearly always unusable in revision cases, where prior cuts and component removal distort the anatomy.
This paper gives you a concrete decision rule: when posterior condyles cannot be used, identify the surgical epicondylar axis (lateral prominence to medial sulcus) and dial in 3.5° of external rotation for males and essentially 0° for females relative to that axis.
Do not apply a generic "3 degrees external rotation" rule to everyone. Female anatomy sits nearly parallel to the surgical epicondylar axis, and over-rotating a female femoral component is a real intraoperative error this paper prevents.
This work became the anatomic foundation for epicondylar-axis-based referencing in computer navigation and patient-specific instrumentation. You will see this axis called out explicitly in modern TKA systems.