Table 3.

Previous studies highlighting the variations of knee angles in healthy children of different ethnic groups

Title	Authors (year)	Number of children	Age composition	Results	Conclusion
Angular and rotational profile of the lower limb in 2,630 Chinese children [4]	Cheng et al. (1991)	2,630	Newborn to 12 years of age	Most newborns had bowlegs, with a mean ICD of 3 cm, ranging from 0 to 5.5 cm. At 1 year of age, the ICD decreased to a mean of 0 cm, followed by a knock-knee phase with the maximum IMD of 2.8 cm at age 3 years, followed by gradual reversion back to the plateau of 0 cm at age 8 years	The largest study carried out to date in the Chinese population. It recorded bowlegs (varus) at birth, genu rectus at 1 year, maximum valgus at 3 years, and a rapid decrease in the mean IMD after 3 years of age in Chinese children, reaching 0 cm at age 8 years, with a normal range of ±3 cm
Knee angles and rickets in Nigerian children [11]	Oginni et al. (2004)	2,036	Newborn to 12 years of age	The majority of the knees were bowed (varus) in the first 6 months. At 21–23 months, the distribution of angles became strongly bimodal: about half being varus and half being valgus (knock-kneed). After this, the knee angle was found to be valgus in most of the children	Change from varus to valgus in individual infants might be sudden (a few weeks), although this changeover of the whole population appeared smooth and gradual. Varus knee alignment was uncommon after 2 years of age in Nigerian children and large knee angles between 2 and 5 years of age suggested rickets
The development of the tibiofemoral angle in children [5]	Salenius and Vankka (1975)	1,279	Newborn to 16 years of age	Pronounced varus position was recorded before the age of 1 year, which changed in valgus between 18 months and 3 years of age. After that, the valgus corrected spontaneously to about 5–6°. No gender variation was seen	There is a wide range of normal development of the knee angle which is physiological, so an operative procedure to correct the angle in normal children is seldom indicated
Normal development of the tibiofemoral angle in children: a clinical study of 590 normal subjects from 3 to 17 years of age [10]	Arazi et al. (2001)	590 Turkish children	3–17 years of age	Children aged between 3 and 17 years were found to exhibit up to 11° physiologic valgus. The maximal mean valgus angle was 9.6° at 7 years of age for boys and 9.8° at 6 years of age for girls	A measurable varus angle or a valgus angle higher than 11° only should be considered as abnormal. These higher normal values should be considered as racial differences between Turkish children and those of other races
Development of tibiofemoral angle in Korean children [9]	Yoo et al. (2008)	818 limbs (433 boys and 385 girls)	Younger than 16 years old	Genu varum was found before 1 year of age, progressing to neutral at 1.5 years of age. This was followed by increasing genu valgum, with a maximum of 7.8° at 4 years, followed by a gradual decrease to approximately 5–6° of genu valgum of the adult level at 7–8 years of age	Overall patterns of the chronological changes in the knee angle were similar to those described previously in western or Asian children, but the knee angle development was delayed
Normal limits of knee angle in white children—genu varum and genu valgum [3]	Heath and Staheli (1993)	196	6 months to 11 years	Maximum bow-leg was noted at an age of 6 months, which progressed towards neutral knee angles by the age of 18 months. The greatest mean knock knee of 8° was found at an average age 4 years, followed by a gradual decrease to a mean of <6° at 11 years of age	The presence of varus during the ages 2–12 years is considered as abnormal. Normal children also display ICDs <3 cm and IMDs <8 cm
Development of the clinical tibiofemoral angle in normal adolescents. A study of 427 normal subjects from 10 to 16 years of age [13]	Cahuzac (1995)	427	10–16 years	Girls were found to have a constant valgus and displayed an IMD <8 cm or an ICD <4 cm. Contrary to this, boys had a varus evolution (4.4°) during the last 2 years of growth and displayed an IMD <4 cm or an ICD <5 cm	The development of the TFA follows different paths in boys and girls between 10 and 16 years of age