Birth defects, also called congenital anomalies, are physical abnormalities that occur before a baby is born. "Congenital" means "present at birth." (See also Introduction to Birth Defects of the Face, Bones, Joints, and Muscles Introduction to Birth Defects of the Face, Bones, Joints, and Muscles Birth defects, also called congenital anomalies, are physical abnormalities that occur before a baby is born. "Congenital" means "present at birth." Birth defects of the face and limbs are fairly... read more .)
The femoral head is the top part of the thighbone (femur), the largest bone in the leg. The femoral head may be twisted (called torsion) either internally (the knees point toward each other with toes in, called internal torsion) or externally (the knees point in opposite directions, called external torsion). The twisting appears to be related to the position the baby is in while it is growing in the uterus. Because it often runs in families, some people may be genetically predisposed to this condition. Twisting of the femoral head is common among newborns.
Doctors can detect this birth defect by laying the infant on an examining table and rotating the hips in different directions, noting whether movement is limited. Infants with severe external torsion often have ultrasonography or x-rays of the hip to look for congenital hip dislocation Developmental Dysplasia of the Hip Developmental dysplasia of the hip is a birth defect in which the bones in the hip are incorrectly developed. Birth defects, also called congenital anomalies, are physical abnormalities that... read more 
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Treatment of Femoral Torsion
Sometimes surgery
By adolescence, internal torsion tends to gradually decrease without treatment. Consultation with an orthopedist and surgery are usually needed for children who have a spinal defect, such as spina bifida Spina bifida Neural tube defects are a certain type of birth defect of the brain, spine, and/or spinal cord. Neural tube defects can result in nerve damage, learning disabilities, paralysis, and death. The... read more , or those in whom the torsion interferes with the ability to walk.
External torsion typically corrects itself, especially after the child begins to stand and walk. However, consultation with an orthopedist is needed if external torsion persists after age 8 because at that point the child may need surgery to correct it.
