Knocked Knees (Genu Valgum) at Age 4 is Completely Normal
Knocked knees at 4 years of age represent the peak of normal physiological development and require no intervention. This is the expected alignment pattern in healthy children at this age 1, 2.
Normal Developmental Pattern of Lower Limb Alignment
The lower extremities follow a predictable developmental sequence that every clinician should recognize:
- Birth to 18 months: Children are physiologically bowlegged (genu varum), with maximum bowing at 6 months of age 1.
- 18 months to 2 years: The legs progress toward neutral alignment (0 degrees) 1.
- 2 to 4 years: Progressive knock-knee (genu valgum) develops, reaching maximum valgus of approximately 8 degrees at age 4 years 1, 3.
- 4 to 11 years: Gradual decrease in valgus occurs, stabilizing to less than 6 degrees by age 11 years 1.
- Skeletal maturity: Final alignment shows only minor degrees of valgus, typically 4-5 degrees 3.
What is Normal at Age 4?
At 4 years old, the following measurements are within normal limits:
- Knee valgus angle up to 12 degrees is normal 1.
- Intermalleolar distance (IMD) up to 8 cm is acceptable 1.
- The prevalence of physiological knock-knee in 3-4 year olds is approximately 64%, decreasing to 44% by ages 4-5 years 4.
When to Worry: Red Flags
Bowlegs (genu varum) after age 2-3 years is abnormal and warrants evaluation, as this represents persistence beyond the normal developmental window 1, 3. However, knock-knee at age 4 is the opposite concern and is expected.
Clinical Significance
Children with physiological knock-knee at this age may demonstrate:
- Shorter stride length and slower walking speed compared to children without knock-knee 4.
- Dynamic knee hyperextension of approximately 8 degrees during gait 4.
- These gait variations are part of normal development and resolve as the child matures 4.
Management Approach
No treatment is necessary for physiological knock-knee at age 4 years 2. Historical treatments with special shoes, braces, or other contraptions have been proven superfluous and do not alter the natural history 2. Reassurance to parents is the appropriate intervention.
Common Pitfalls to Avoid
- Do not initiate treatment for normal physiological valgus at age 4 - this represents unnecessary intervention that will not change the natural developmental course 2.
- Do not confuse genu valgum (knock-knee) with genu varum (bowlegs) - the question mentions "genu varum" but asks about knocked knee, which is actually genu valgum. At age 4, valgum is normal while varum would be abnormal 1, 3.
- Consider evaluation only if valgus persists beyond age 10-11 years with measurements exceeding normal limits, or if asymmetric deformity is present 1.