Femoral Anteversion vs Retroversion: Definitions
Femoral anteversion refers to the forward (anterior) rotation of the femoral neck relative to the femoral shaft and knee axis, while femoral retroversion describes backward (posterior) rotation of the femoral neck relative to these same reference points.
Anatomical Definition
Femoral anteversion is the angle between the femoral neck axis and the transverse axis of the femur (typically measured using the posterior femoral condyles or transepicondylar axis as reference) 1, 2. This represents the degree of torsion present in the femur.
Key Measurement Points:
- Anteversion (positive values): The femoral neck is rotated anteriorly (forward) relative to the knee axis
- Retroversion (negative values): The femoral neck is rotated posteriorly (backward) relative to the knee axis
- Neutral (0 degrees): The femoral neck axis is aligned with the transverse knee axis
Normal Values and Population Variation
The traditional teaching of "15 degrees of anteversion" as a population norm is not universally applicable and shows significant geographic and demographic variation:
- Western populations: Mean approximately 15 degrees of anteversion 3
- Indian/Asian populations: Mean -2.6 degrees (actually retroversion), with 53.2% showing retroversion 4
- General range: -10 to +41 degrees in healthy adults 5
Important clinical caveat: Individual variation is substantial, with up to 30-degree differences within apparently healthy adults 1. Approximately 12.5% of individuals may have femoral retroversion 5.
Sex and Age Differences
- Women demonstrate significantly higher anteversion than men (mean difference approximately 6 degrees) 4, 6
- Age effects: Anteversion increases substantially during gestation, then decreases steadily until maturity 1. In adulthood, femoral anteversion decreases approximately 0.30 degrees per year while acetabular anteversion increases 0.12 degrees per year, though combined anteversion remains stable 6
Biomechanical Significance
Femoral anteversion directly affects:
- Hip biomechanics: Alters moment arm lengths and joint loading patterns 1
- Anterior offset: Increasing anteversion by 1 degree increases anterior offset by approximately 0.6-0.7mm 7
- Femoral rotation: Increasing anteversion by 4 degrees produces approximately 1 degree of internal femoral rotation 7
- Gait patterns: Altered gait associated with abnormal anteversion may contribute to osteoarthritis development 1
Clinical Implications
The contralateral femur is a more reliable reference than population norms: Studies show mean interfemoral rotational variance of only 5.3 degrees compared to 8.2 degrees variation from the assumed 15-degree population mean 8. Only 5% of patients have >15 degrees difference between sides, while 15% vary >15 degrees from the population mean 8.
This has critical implications for surgical planning, particularly in total hip arthroplasty and femoral fracture management, where individualized assessment based on CT imaging is superior to assuming population norms 4, 7, 8.