Stylized knee joint with internal gears representing knee mechanics and ethnic silhouettes symbolizing anatomical variation.

Knee Torsion Varies by Ethnicity: Why It Matters for Joint Replacements

Beau Callahan in Health & Wellness December 2025 • 4 min read.

"New research highlights the importance of considering ethnic differences in distal femoral torsion for better knee replacement outcomes."

Total knee arthroplasty (TKA) aims to relieve pain and restore function in individuals with severe knee joint damage. Achieving optimal alignment of the femoral component is critical for long-term implant survival and functional outcomes. Proper alignment directly influences the biomechanics of the knee, affecting both stability and patellar tracking.

Key to femoral component positioning is understanding distal femoral torsion (DFT), the angle between the posterior condylar axis (PCA) and the transepicondylar axis (TEA). The TEA, encompassing the anatomical and surgical epicondylar axes, serves as a reference point. While the surgical TEA guides prosthesis rotation, the anatomical TEA is more reliably measured through imaging. Understanding the nuances between these measurements is vital for precise TKA.

While individual variation in DFT is well-documented, the potential influence of ethnicity has been largely unexplored. A recent study comparing the 3D morphology of the distal femur between Caucasian and Asian populations revealed distinct differences, prompting further investigation into DFT variations between these groups. This research aims to address that gap, analyzing DFT values in non-arthritic knees across different ethnicities, ages, sexes, and sides of the body.

Distal Femoral Torsion (DFT): What the Study Revealed

Stylized knee joint with internal gears representing knee mechanics and ethnic silhouettes symbolizing anatomical variation.

A comprehensive study was conducted using computed tomography (CT) scans of distal femurs from 515 patients. The study group comprised 259 Asian patients (from China) and 256 Caucasian patients (from France). Exclusion criteria ensured that all patients had healthy knees without any signs of osteoarthritis or bone pathologies. Researchers carefully measured the anatomical distal femoral torsion (TEFD) and analyzed its relationship with ethnicity, age, sex, and laterality.

Key findings from the study include:

Significant Ethnic Variation: Asians exhibited a significantly greater mean TEFD (6.4°) compared to Caucasians (5.5°). This difference highlights the need to consider ethnicity in preoperative planning.
No Impact from Age, Sex, or Laterality: The study found no significant correlation between TEFD and factors like age, sex, or whether it was the left or right knee.
Reliable Measurements: The measurement techniques employed demonstrated low inter- and intra-observer variability, ensuring the reliability and accuracy of the results.

These findings support the hypothesis that TEFD is subject to inter-ethnic variability. This variability, combined with known inter-individual differences, emphasizes the importance of individualized assessments before total knee arthroplasty.

Personalized Approaches: The Future of Knee Replacements

This research underscores the importance of recognizing ethnic variations in knee anatomy for optimizing outcomes in total knee arthroplasty. By considering these differences and employing precise measurement techniques, surgeons can better personalize procedures, potentially reducing complications and improving patient satisfaction. Preoperative CT or MRI scans are valuable tools for accurately assessing TEFD and guiding the rotational alignment of the femoral component. Further research is needed to explore the clinical implications of these findings and develop tailored surgical approaches that account for ethnic-specific anatomical variations.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1016/j.rcot.2018.09.008, Alternate LINK

Title: Variabilité Interethnique De La Torsion Fémorale Distale (Caucasiens Versus Asiatiques). Étude Multicentrique De 515 Scanners Du Fémur Distal

Subject: Orthopedics and Sports Medicine

Journal: Revue de Chirurgie Orthopédique et Traumatologique

Publisher: Elsevier BV

Authors: Jérôme Murgier, Élodie Chantalat, Ke Li, Philippe Chiron, Norbert Telmon, Wei Huang, Émilie Berard, Etienne Cavaignac

Published: 2018-11-01

Everything You Need To Know

What is distal femoral torsion, and why is it important in knee replacement surgery?

Distal femoral torsion (DFT) refers to the angle between the posterior condylar axis (PCA) and the transepicondylar axis (TEA) in the femur. Understanding DFT is crucial in total knee arthroplasty (TKA) because it helps surgeons properly align the femoral component of the knee implant. Proper alignment directly influences the biomechanics of the knee, affecting both stability and patellar tracking. In TKA, achieving optimal alignment is critical for long-term implant survival and functional outcomes.

What did the study discover about differences in knee torsion between different ethnic groups?

The study revealed that Asians, specifically those studied from China, have a significantly greater mean transepicondylar femoral distance (TEFD) (6.4°) compared to Caucasians (5.5°). This means that there's a notable difference in the average angle of the distal femur between these two ethnic groups. This finding is important because it suggests that a one-size-fits-all approach to knee replacement surgery may not be optimal, and considering ethnicity in preoperative planning is essential for better outcomes.

What is the transepicondylar axis, and what role does it play in knee replacement surgery?

The transepicondylar axis (TEA) is a reference point used in total knee arthroplasty (TKA) to guide the rotational alignment of the femoral component. There are two types: the anatomical TEA, which can be reliably measured through imaging, and the surgical TEA, which guides prosthesis rotation during surgery. Understanding the difference is vital for precise TKA, ensuring optimal biomechanics and function of the replaced knee joint. The anatomical TEA is used for pre-operative planning and the surgical TEA is used as a guide in the surgery itself.

How did the researchers measure distal femoral torsion in the study, and what steps did they take to ensure the accuracy of their results?

The study utilized computed tomography (CT) scans to measure the anatomical distal femoral torsion (TEFD) in a group of 515 patients, comprising 259 Asian patients (from China) and 256 Caucasian patients (from France). By excluding patients with signs of osteoarthritis or bone pathologies, researchers ensured they were analyzing healthy knees. The measurements focused on assessing the relationship between TEFD and factors like ethnicity, age, sex, and which knee was being examined. The study's rigorous methodology and attention to detail are what made the result reliable.

What does it mean to have a personalized approach to knee replacement, and how does it relate to this research?

Personalized approaches in total knee arthroplasty (TKA) means that surgeons consider individual and ethnic variations in knee anatomy, particularly distal femoral torsion (DFT), to optimize surgical outcomes. This involves using preoperative CT or MRI scans to accurately assess TEFD and guide the rotational alignment of the femoral component. By tailoring the surgical approach to each patient's specific anatomy, surgeons aim to reduce complications, improve implant survival, and increase patient satisfaction. Further research is needed to develop even more tailored surgical techniques that account for these anatomical variations.