What causes asymmetrical thigh creases?

Asymmetric leg creases are commonly observed in some newborns. Normally, these creases should be symmetrical; however, asymmetry may indicate underlying conditions—such as congenital hip dislocation—that require medical attention. If asymmetry is noted, prompt evaluation at a hospital is recommended to determine the specific cause. Below, we address the question: “What causes asymmetric leg creases?”

What Causes Asymmetric Leg Creases?

New mothers can gently hold their baby’s feet symmetrically and carefully observe the skin creases on the thighs and around the buttocks to assess symmetry. Approximately 90% of infants exhibit some degree of leg crease asymmetry—particularly chubby babies, who are more prone to this phenomenon. Thus, asymmetric leg and gluteal creases are extremely common during infancy. However, only a very small proportion of infants with asymmetric creases actually have hip joint developmental abnormalities. In other words, asymmetric leg creases do not necessarily indicate abnormal hip development—but abnormal hip development may manifest as asymmetric leg creases.

Knowledge Extension: How to Screen for Developmental Dysplasia of the Hip (DDH) in Children

1. Comparison of Leg Length

Parents can hold their child upright at home and compare the lengths of both legs. Even if leg creases appear normal and symmetrical, developmental dysplasia of the hip (DDH) may still be present; limb-length discrepancy is sometimes a prominent sign.

2. Frog-Leg Test

Lay the baby supine on a flat surface, flex the hips and knees to 90°, then gently abduct the legs outward. In healthy infants, both knees should comfortably touch the surface. Parents need not worry about causing injury—the infant’s bones remain soft and pliable at this age, making such maneuvers safe.

3. Timely Intervention Is Critical in Severe Cases

If DDH is suspected, do not assume that simple home exercises or self-management will suffice. Delaying professional evaluation due to overconfidence may miss the optimal window for intervention. Prompt recognition and immediate consultation with a pediatric orthopedic specialist are essential.

The above outlines the causes and implications of asymmetric leg creases. We hope this information proves helpful.