Development of the tibiofemoral angle in a cohort of Nigerian children during the first 3 years of life

Purpose Findings from cross-sectional studies of knee angle development in Nigerian children vary in values and in the age at which the varus angle changes to the valgus angle. This study was conducted to describe knee angle development and to determine the age when the knee angle changes from the varus to the valgus angle. Methods This was a longitudinal survey of 152 Nigerian children recruited within 3 weeks of life and followed up monthly until age 3 years. Their knee angle was measured using clinical methods. Results The mean tibio-femoral/varus knee angle (13.2 +/- 3.8 degrees) at birth-3 weeks of life decreased sharply to 5.6 +/- 0.7 degrees at 9 months, increased slightly to 6.3 +/- 1.1 degrees at 13 months, and then decreased again up to age 18 months (0.3 +/- 2.1 degrees). The mean valgus knee angle increased from -2.4 +/- 2.5 degrees at 19 months of life to -8.5 +/- 2.5 degrees at 27 months and then decreased to -7.7 +/- 2.2 degrees at 36 months. Intercondylar/ intermalleolar distances ( ICD/ IMD) showed a similar pattern, changing from an extreme varus knee (ICD) at birth- 3 weeks of life (2.5 +/- 0.7 cm), decreasing to 0.6 +/- 0.2 cm at 9 months, increasing to 0.8 +/- 0.5 cm at 12 months, and decreasing to 0.1 +/- 0.4 cm at 15 months. The mean IMD increased from - 0.1 +/- 0.8 cm at 16 months of life to - 2.0 +/- 1.5 cm at 29 months and then decreased up to 36 months. Our tri-modal analysis showed that the transition from the varus to the valgus angle was between 18 and 19 months. Conclusion Our findings suggest that the developmental pattern of the knee angle in Nigerian children is at maximal varus at birth, neutral at 18 months of life, and valgus at 19 months, with the valgus angle continuing to increase up to 36 months.