Overview
Bow legs (genu varum) and knock knees (genu valgum) are common leg alignment variations that occur during childhood growth and development. Bow legs are characterized by outward curving of the legs, creating a noticeable gap between the knees when the ankles are together. Knock knees, on the other hand, occur when the knees touch or angle inward while the ankles remain apart.
These conditions are usually part of normal growth and often self-correct as children grow older. However, persistent, severe, or asymmetrical cases may signal underlying bone, joint, or metabolic conditions that require medical attention.
Commonly Associated
Other names and related terms include:
- Genu varum – bow legs
- Genu valgum – knock knees
- Physiologic bowing – normal developmental bowing in toddlers
- Pathologic genu varum/valgum – bow legs or knock knees caused by underlying disease
Causes
Most cases are normal developmental variations, but they can also result from specific conditions:
- Physiological development – Bow legs are normal in infants and toddlers up to around age 2, and knock knees often appear between ages 3 and 5.
- Bone growth patterns – Rapid growth phases can temporarily alter leg alignment.
- Nutritional rickets – Vitamin D or calcium deficiency affecting bone strength and shape.
- Blount’s disease – A growth disorder affecting the shinbone (tibia), leading to severe bowing.
- Skeletal dysplasia – Genetic bone development disorders such as achondroplasia.
- Previous trauma or infection – Injury or bone infection affecting growth plates.
- Obesity – Extra weight can place stress on developing legs, worsening misalignment.
Symptoms
While many children show no discomfort, symptoms can include:
- Visible outward (bow legs) or inward (knock knees) leg curvature
- Uneven gait or limping
- Pain in knees, hips, or ankles (in severe cases)
- Difficulty walking or running
- Uneven shoe wear due to altered weight distribution
- Progressive worsening of leg alignment over time
Exams & Tests
Diagnosis typically involves a combination of physical examination and imaging:
- Physical exam – Measures leg alignment, knee angle, and walking pattern.
- Measurement of intermalleolar (knock knees) or intercondylar (bow legs) distance – Determines severity.
- X-rays – Evaluate bone growth, alignment, and identify underlying disorders like Blount’s disease.
- Blood tests – May be used to check for rickets or other metabolic conditions.
- Growth monitoring – Regular check-ups to observe changes over time.
Treatment
Treatment depends on the severity, age, and cause of the condition:
- Observation – Most mild cases resolve naturally as the child grows.
- Bracing or orthotics – May be used in certain cases (e.g., Blount’s disease).
- Nutritional supplementation – Vitamin D and calcium if rickets is present.
- Physical therapy – To improve strength, balance, and gait.
- Surgery (osteotomy or guided growth) – Considered in severe, persistent, or progressive cases to correct alignment.
With proper diagnosis and management, most children achieve normal leg alignment and function as they grow older.
Source of Bow Legs and Knock Knees in Children and Young People
- American Academy of Orthopaedic Surgeons (AAOS) – Pediatric Lower Limb Alignment
- NHS – Bow Legs and Knock Knees in Children
- Mayo Clinic – Genu Varum and Genu Valgum Overview
