What is the normal intermalleolar distance range at 4 years of age and how is it measured?

Measuring Intermalleolar Distance at 4 Years of Age

Measure intermalleolar distance (IMD) by having the child stand erect with knees fully extended and medial malleoli (inner ankle bones) touching, then measure the distance between the medial femoral condyles at their closest point. 1

Measurement Technique

• Position the child standing upright with both legs together, ensuring the medial malleoli are in contact with each other 1
• Keep the knees fully extended (straight) during measurement 1
• Measure the shortest distance between the medial femoral condyles (the bony prominences on the inner aspect of the knees) 1
• Document the measurement in centimeters alongside height and growth velocity for comprehensive tracking 1, 2

Normal Range at 4 Years

At 4 years of age, the normal intermalleolar distance is up to 8 cm, with the greatest mean knock-knee angle of approximately 8 degrees observed at this age. 3, 4

• Children aged 2-11 years can have knock-knee up to 12 degrees with intermalleolar distance up to 8 cm and still be considered normal 3
• The maximum tibiofemoral angle at 4 years is approximately 7.6° ± 2.4°, representing the peak of physiological genu valgum (knock-knee) 4
• Prevalence of physiological knock-knee at ages 3-4 years is approximately 64%, decreasing to 44% at ages 4-5 years 5

Critical Clinical Caveats

• Any bowlegs (genu varum) after age 2 years is abnormal and requires evaluation for metabolic causes such as X-linked hypophosphatemia, rickets, or Blount disease 3, 2
• Asymmetric deformities (one leg bowed inward, the other outward) require immediate orthopedic referral 2
• IMD measurements alone cannot replace comprehensive orthopedic assessment, as they do not capture limb torsion, rotational abnormalities, or combined deformities 2
• Persistent or worsening intermalleolar distance beyond expected physiological ranges suggests pathologic conditions requiring biochemical evaluation 2, 6

Serial Monitoring Strategy

• Measure IMD at each clinical visit to track progression or improvement 1, 2
• Document measurements alongside height, weight, and growth velocity for comprehensive assessment 1
• Changes in IMD help evaluate response to treatment in metabolic conditions like X-linked hypophosphatemia 1, 2
• Consider radiographic evaluation with standardized anterior-posterior standing limb alignment films if clinical concerns persist 1