The young girl may have a condition called Blount disease. Curvature or bowing of the lower leg is usually present in young children. This comes from the position they were in while in utero (in the uterus). The legs start to straighten out once the muscles of the lower back and legs are strong enough to hold the child in the upright position.
With Blount disease there is abnormal growth of the bone causes the bowing to get worse instead of better over time. There is abnormal compressive forces across the growth plate of the tibia (lower leg bone). Growth is stopped and deformities can occur.
There are three types of tibia varum based on the age it begins: 1) infantile (less than three years old), 2) juvenile (occurs between four and 10 years), and 3) adolescent (11 years of age and older).
About 40 per cent of the children with Blount disease develop it at a later age. It occurs during late childhood and early adolescence when growth is most likely to take place.
We don’t really know what triggers Blount disease. Juvenile or adolescent Blount disease is usually caused by obesity (being overweight). But it can also be the result of infection or trauma that disrupted the medial growth plate. The fact that not all overweight children develop Blount disease suggests other factors as well.