What to Know About Bow Legs

Medically Reviewed by Dan Brennan, MD on February 15, 2024
3 min read

Bow legs (also known as "genu varum") occur when a person's legs bend outward and don't touch at the knees, even if their feet and ankles remain together. If left undiagnosed in childhood, bow legs can lead to arthritis and other pain conditions. People with bow legs are often referred to as bowlegged.

Some babies are born with bow legs because of the way their legs were folded to fit inside the small space of the womb. 

The bowing effect can sometimes increase a little when a child is learning to walk, but it should get better. If your child started walking at a younger age, they will have more obvious bow legs. The condition usually goes away, though, by the time a child is three or four years old. 

‌Other causes of bow legs include:

  • Blount's disease. Blount’s disease happens when growth plates around the knee either slow down or stop making new bone while growth plates near the outside of the knee continue developing as normal. Blount’s disease can happen between birth and age 3, and it usually occurs in both knees. Adolescent Blount’s disease affects children over age 10 and is likelier to affect just one knee.
  • Rickets. Rickets is a bone disease caused by a lack of calcium, phosphorus, or vitamin D, all of which are needed to grow strong bones. It's rare to get rickets in a developed country because many food products are fortified with vitamin D, but the condition can also be triggered by a genetic problem that stops vitamin D from being absorbed properly.
  • Knee injury or infection

Bow legs appear to be bent outward, or bowed, even when the feet and ankles are held together. There's usually a clear space between the lower legs and knees. 

Other symptoms of bow legs include:

  • Unstable knees
  • Reduced motion in the hips
  • Knee or hip pain

When diagnosing a bow leg deformity, your doctor will look through your child's patient history, conduct a physical examination, and order an X-ray of their leg bones from hip to ankle.

The earlier that bow leg deformity is diagnosed, the better. Adults who were not diagnosed with bow leg deformity as a child often develop progressive knee arthritis, and those who have lived with bow legs for many years may experience leg pain and instability.

It's normal for babies and young toddlers to have bow legs, but if your child has the condition beyond the age of three, you should see a doctor, as the child might have bow leg deformity. Bow legs don't cause pain or discomfort at a young age, though, and won't limit your child's ability to walk, crawl, or run. 

The recommended treatment for bow legs depends on the underlying cause of the condition, and can include:

  • A leg brace
  • Surgery
  • Endocrinological treatment

A child with Blount's disease is usually treated with either a leg brace or surgery. The brace used is called a modified knee-ankle-foot orthosis (KAFO) and must be worn both day and night. It works by releasing compression in the knee to encourage your child's leg to grow normally. 

Your doctor may suggest surgery if the KAFO brace alone doesn't work.

Additionally, if your child is still growing, a minimal-incision surgical procedure can encourage their leg to become straight. For bowlegged teens and adults, a type of surgery called osteotomy, in which one or more bones are cut, could also help. 

Your doctor will use X-ray imaging to gauge how severe the deformity is and where it's located. If the deformity is moderate, the bone can be stabilized using an internal plate or rod post-surgery. If the deformity is severe, external pins are inserted into the bone, with the other end attaching to a stabilizing structure outside the body. 

In cases where the bow leg deformity makes one leg shorter than the other, limb lengthening surgery may be recommended.

If bow legs are the result of a genetic case of rickets, your child will need specialized treatment from an endocrinologist.