Knee angles and rickets in Nigerian children

Knee angles of 2,036 normal Nigerian children up to 12 years old were measured directly or from photographs. The knees were bowed (varus) in the first 6 months. At 21 to 23 months, the distribution of angles became strongly bimodal: about half were varus and half were valgus (knock-kneed), with few in between. After this they were all valgus, with few exceptions. Hence, the change from varus to valgus in individual infants must be sudden (a few weeks), although the changeover of the whole population appears smooth and gradual. They became maximally and uniformly knock-kneed (-7.1degrees +/- 1.4degrees) between 3 and 3.5 years, with little change thereafter. On the other hand, 120 patients with rickets discovered during screening had large knee angles, in either sense, with a bimodal distribution and frequency maxima at + 10degrees (varus) and - 12degrees (valgus). Varus knee is uncommon after 2 years. Large knee angles between 2 and 5 years suggest rickets.