Clinical Knee Alignment among Adolescents and Association with Body Mass Index: A Large Prevalence Study.

BACKGROUND: Children and adolescents are commonly referred to an orthopedic surgeon to assess knee malalignment.

OBJECTIVES: To assess the prevalence of genu varum and valgum among adolescents, and to identify correlates of these conditions.

METHODS: A medical database of 47,588 candidates for military service presenting to the northern recruitment center during an 11 year period was analyzed to identify clinical knee alignment. Based on the standing skin surface intercondylar distance (ICD) or intermalleolar distance (IMD), the prevalence rates of genu varum (ICD ≥ 3 cm) and genu valgum (IMD ≥ 4 cm) were calculated. The association of gender, body mass index (BMI), and place of residence to knee alignment was studied.

RESULTS: The rates of genu varum and valgum were 11.4% (5427) and 5.6% (2639), respectively. Genu varum was significantly more prevalent among males than females (16.2% vs. 4.4%, P < 0.001). It was also more prevalent among underweight subjects and less prevalent among overweight and obese subjects (P < 0.001). Genu valgum was significantly more prevalent among females than males (9.4% vs. 2.9%) and in overweight and obese subjects compared to those with normal BMI, while less prevalent in underweight subjects (P < 0.001). Multivariate analysis revealed that genu varum was independently positively associated with male gender, underweight, and living in a rural area. Genu valgum was independently positively associated with female gender, overweight, and obesity.

CONCLUSIONS: This study establishes a modern benchmark for the cutoff and prevalence of genu varum and valgum as well as associations with gender and BMI.