Bow Legs and Knock Knees: Normal Growth or a Problem?

Parents often worry when a toddler's legs look bent. Most of the time this is part of normal growth. But some bowing or knock knees are caused by disease, get worse with age, and need treatment. This article explains how to tell the difference.

Normal leg shape changes with age

• Birth to about 2 years: mild bow legs are normal
• About 3–4 years: legs often swing the other way into mild knock knees
• By about 7–8 years: most children settle into the straight, adult alignment

Warning signs – see a specialist if

• Bowing is severe, or worsening after age 2
• Knock knees are severe, or persist after age 7–8
• Only one leg is affected
• The child is very short for age, has pain, limps, or tires easily
• Wrist or rib swelling, delayed walking or dental problems (possible rickets)
• A family history of bone disease

Common causes of abnormal bowing or knock knees

• Rickets – vitamin D or calcium deficiency, or inherited phosphate-losing (hypophosphataemic) rickets
• Blount's disease – abnormal growth at the inner part of the upper shin
• After injury or infection that damaged a growth plate
• Skeletal dysplasias such as achondroplasia
• Adults: old fractures that healed crooked, or deformity that has led to knee arthritis

How we evaluate

1. Examination standing and walking; measuring the gap between knees or ankles
2. Full-length standing X-ray of both legs to measure the mechanical axis and find the level of deformity
3. Blood tests when rickets is suspected: calcium, phosphate, alkaline phosphatase, vitamin D, kidney function
4. Computer-assisted deformity planning when correction is needed

Treatment options

• Observation for normal, age-appropriate shapes
• Medical treatment of rickets – mild deformities often improve once the cause is treated
• Guided growth – in growing children, a small plate on one side of the growth plate lets the other side catch up, gradually straightening the leg through a small incision
• Osteotomy – cutting and realigning the bone, either at once with a plate or nail, or gradually with an Ilizarov or hexapod frame for large or multi-level deformities and when length must also be corrected
• Adults with early knee arthritis from bowing may benefit from a realignment osteotomy around the knee to shift weight to the healthier side

Recovery

Guided growth usually means a short hospital stay and quick return to school, with regular X-rays until the leg is straight. Osteotomy needs a few weeks of protected weight-bearing and physiotherapy; gradual correction takes longer but allows very precise final alignment.

Frequently asked questions

Will special shoes or massage straighten the legs? No. Shoes, braces or massage do not correct bony bowing.

Is surgery safe in small children? Guided growth is minimally invasive, but the timing depends on how much growth is left. We plan it carefully.

Can the deformity come back? Yes, especially in untreated rickets or Blount's disease, which is why follow-up continues until growth ends.