In a 9‑month‑old female infant with an asymmetric medial lower left leg skin fold that does not encircle the leg, normal developmental milestones, and no history of developmental dysplasia of the hip, what is the appropriate management?

Reassurance and Observation Without Imaging

In this 9-month-old infant with an isolated asymmetric medial lower leg skin fold, normal hip examination, normal developmental milestones, and no hip dysplasia concerns, no further evaluation or imaging is indicated—reassurance is appropriate.

Clinical Reasoning

Asymmetric Skin Folds Lack Specificity for DDH

The evidence consistently demonstrates that asymmetric skin folds have extremely poor predictive value for developmental dysplasia of the hip (DDH). Multiple high-quality studies show:

• Positive predictive value of only 4.55% to 4.79% for DDH when asymmetric skin folds are the sole finding 1, 2
• When isolated asymmetric thigh creases were the only clinical sign in 117 infants, the positive predictive value was just 4.55%, with a specificity of 82% 2
• In a large series of 584 infants referred for DDH screening, 78.4% were referred for asymmetric skin folds alone, yet none were diagnosed with DDH 3
• Another study of 105 patients with asymmetric skin creases found 0% positive predictive value when specialist hip examination was otherwise normal 4

Guidelines Emphasize Limited Clinical Significance

The ACR Appropriateness Criteria explicitly state that "asymmetric skin folds in the proximal thigh and shortening of the limb on the dislocated side lack specificity for the diagnosis of DDH" 5. This finding is considered unreliable as a screening tool, particularly when:

• The hip examination is normal (no limited abduction, no Galeazzi sign, no instability)
• The infant has achieved normal developmental milestones (crawling, pulling to stand)
• There are no other risk factors present

Age-Appropriate Screening Considerations

At 9 months of age, this infant is well beyond the typical screening window:

• Hip examination remains the primary screening method at every well-baby visit 5
• After 2-3 months of age, Ortolani and Barlow maneuvers become less sensitive, and limited hip abduction becomes the most important physical finding 5
• The AAP and AAOS do not advocate ultrasound screening after 4-5 months of age 5
• If imaging were indicated at this age, pelvic radiography would be preferred over ultrasound 5

Key Clinical Pitfalls to Avoid

Don't Over-Interpret Provocative Skin Folds

One important study found that 82% of infants with apparent asymmetric thigh creases developed provocative skin creases on the opposite side with gentle pressure during examination 2. This suggests many "asymmetric" findings are actually normal variants that can be elicited bilaterally.

Distinguish Location: Lower Leg vs. Hip Region

The guidelines and research focus on asymmetric skin folds in the proximal thigh, buttock, and inguinal regions as potential (though unreliable) DDH indicators 5, 4. This infant has a lower leg (medial calf) skin fold, which is even further removed from hip pathology and has no established association with DDH.

Focus on Meaningful Clinical Signs

If DDH were present at 9 months, you would expect to find:

• Limited hip abduction (the most important finding after 3 months) 5
• Galeazzi sign (apparent leg-length discrepancy with knees flexed) 5
• Delayed or asymmetric motor milestones (not present in this case)

Management Recommendation

Provide parental reassurance that isolated asymmetric skin folds, particularly on the lower leg rather than the thigh, are common normal variants without clinical significance for hip dysplasia 1, 3, 2, 4.

Continue routine well-child care with standard hip examination at scheduled visits, focusing on hip abduction symmetry and developmental milestones 5.

No imaging is warranted given the normal hip examination, normal development, and lack of specific DDH risk factors 5.