Clinical assessment of tibiofemoral angle and its relationship with body mass index

Background: Few studies have investigated BMI as a factor that might influence the physiological development of knee alignment in otherwise healthy normal weight and overweight children and adolescents. Objective: This study set out to determine the relationship between tibiofemoral angle and body mass index in normal children and adolescents in Enugu metropolis. Methodology: This cross-sectional study was done in Enugu metropolis with 3147 school children and adolescents aged 3-17years. The tibiofemoral angle was measured clinically using standard goniometer with extendable arms. The weight, height, BMI percentile-for-age, were determined for all the subjects. The association between tibiofemoral angle and body mass index was then analyzed. Results: Majority of the subjects (97.6%) had valgus TFA. The maximum knee valgus angle was 6.8o±0.80o at 4 years which then declined to a mean of 2⁰ at 17 years. 91.2% of the subjects examined were normal weight(5th-85th percentile), 6.2% underweight(< 5th percentile) and 2.5% overweight( 85th - 95th and > 95th percentile). The tibiofemoral angle was found to have a significant negative correlation with BMI in normal weight and overweight subjects. Conclusions: We found a significant negative correlation between TFA and BMI in normal healthy weight and overweight children and adolescents. Thus, increasing BMI does not cause a corresponding increase in the magnitude of the knee angle.