Appreciation of the differences between the lower extremities of the normal newborn as compared with those of the older child is important in the detection of abnormalities. When compared with older children, normal newborns have greater mobility of the hip, varus alignment of the knee, flatter feet, greater ankle range of motion, and less defined bony prominences.

Lower extremity abnormalities can involve the hip, leg, foot and/or toes and can be positional or structural. While many abnormalities are isolated, some occur with other lower extremity abnormalities or in association with congenital disorders such as myelomeningocele or a congenital myopathy.

It is helpful to think about lower extremity abnormalities as intrinsic or extrinsic. Intrinsic abnormalities are due to characteristics of the infant such as genetic conditions like achondroplasia or osteogenesis imperfecta. Conversely, extrinsic abnormalities are due to in utero conditions such as breech positioning that limit fetal movement, a critical contributor to proper musculoskeletal development. Intrinsic abnormalities are more likely to be due to underlying pathology, whereas most extrinsic abnormalities are positional and resolve spontaneously or respond to surgical correction.

• Female gender, breech positioning, and family history of developmental dysplasia of the hip (DDH) are significant risk factors for DDH.

• 80% of cases of DDH occur in females.

• DDH is more common in first-born infants owing to the relative inelasticity of the primigravid uterus and abdominal wall.

• Native Americans and Laplanders are the ethnic groups at highest risk for DDH, with an incidence of up to 50 in 1,000 live births.

• History of diminished fetal movement for significant periods of time as reported by the mother may be associated with lower extremity abnormalities caused by intrauterine mechanical factors or intrinsic disease of the fetus such as a myopathy, chromosomal abnormality, or myelomeningocele.

• Congenital talipes equinovarus (clubfoot) occurs two to four times more often in males than in females.

• Maternal smoking during pregnancy is a significant risk factor for clubfoot.

• Though polydactyly is most likely to be an isolated trait, it can be inherited in an autosomal dominant manner with variable penetrance.

• Some teratogenic medications taken during pregnancy such as warfarin, methotrexate, and thalidomide are associated with limb anomalies.

• A positive exam for DDH is the palpable “clunk” elicited by the Barlow maneuver (detects the hip subluxing or dislocating from the acetabulum) or Ortolani maneuver (detects reduction of the subluxed or dislocated hip).

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