Leg Deformities in Children (Bow Legs and Knock Knees)
Leg curves in children are often a normal part of growth. Curves that persist beyond certain ages, affect one side or worsen should be assessed.
Leg curves are one of the things parents worry about most. Yet the shape of the legs changes naturally during growth. Bow legs in infancy, knock knees around the age of 3-4 and straightening by school age are part of normal development. The key is telling normal development apart from disease.
Normal development
- Birth to 2 years: Mild bow legs (genu varum) are normal.
- 2-4 years: The legs straighten, then knock knees (genu valgum) may appear.
- 4-7 years: The knock-knee look gradually decreases.
- After 7-8 years: The legs are usually close to their adult shape.
When should it be checked?
- Bow legs that persist or increase after the age of 2-3
- Knock knees that are still marked after the age of 7-8
- A curve in one leg only, or a clear difference between sides
- Being clearly shorter than peers
- Pain, limping or difficulty walking
- A curve that is getting worse quickly
Possible causes
- Physiological (normal) curve: The most common cause
- Rickets: Vitamin D, calcium or phosphate deficiency
- Blount disease: Involvement of the growth area at the top of the shin bone
- Growth plate damage: After a previous fracture or infection
- Skeletal dysplasias and metabolic diseases
Diagnosis
The leg alignment and the distance between the knees and ankles are measured, and walking is assessed. When needed, a standing X-ray of the whole leg shows where the curve is and how severe it is. Blood tests are requested if rickets is suspected.
Treatment
- Monitoring: Physiological curves need no treatment; development is followed at regular intervals.
- Medical treatment: Vitamin and mineral deficiencies are corrected in conditions such as rickets.
- Bracing: May be used in some young children with Blount disease.
- Guided growth: In growing children, a small plate or screw is placed across the growth plate on one side to guide growth. It is done through small incisions, and the leg straightens as it grows.
- Osteotomy: In children who have finished growing or have severe curves, the bone is cut and realigned.
Rickets and nutrition
Rickets happens when bones do not mineralise enough during growth and is one of the preventable causes of leg curves. The most common cause is vitamin D deficiency. Enough sunlight, a balanced diet and regular use of the vitamin D supplement recommended in infancy prevent rickets. Once treated, leg curves often improve markedly with growth.
Blount disease
In Blount disease, the inner part of the growth plate at the top of the shin bone does not grow enough and the bow legs gradually worsen. It is more common in children who walk early and are overweight. Unlike physiological bowing, it does not improve with time but progresses. It is treated with a brace in early stages and surgery in later stages.
How is follow-up done?
Children followed for leg curves are examined at intervals, the distance between the knees and ankles is measured and photographs are compared. X-rays are taken if the curve does not improve as expected. Comparative photos taken at home also help families see the change.
Timing of guided growth surgery
Guided growth can be used while the growth plates are open. The amount of growth remaining determines how long correction will take, so surgery is timed according to the child’s age and skeletal maturity. Once correction is achieved, the implants are removed and growth returns to its natural course.
Frequently asked questions
My baby's legs are bowed. Should I worry?
Mild bow legs are normal in the first 2 years. An assessment is recommended if the curve is marked, one-sided or persists after the age of 2-3.
Do special shoes correct leg curves?
There is no evidence that special shoes or insoles change the leg shape in physiological curves.
Is guided growth surgery a big operation?
It is done through small incisions and usually needs a short hospital stay. The implants are removed once the correction is achieved.
Do leg curves affect walking?
Physiological curves usually do not. With marked curves, the child may tire faster, fall often or have knee pain.
Does sport correct leg curves?
Sport is good for a child's strength and coordination, but it does not change bone curves.
My child is overweight. Does that affect leg curves?
Excess weight increases the load on the knees and can help some curves, especially Blount disease, to progress. Healthy weight control is part of treatment.
Do knock knees cause knee pain?
Marked knock knees can cause pain around the kneecap and the knees rubbing together. Mild, age-appropriate knock knees usually cause no symptoms.
The information on this page is general and does not replace an examination. An examination is needed to decide which treatment suits you.