Knock Knees | Diagnosis & Treatments

How are knock knees diagnosed?

Knock knees become apparent when a child stands with legs straight and toes pointed forward. Your child’s doctor can determine the severity of the knock knees by observing the position of the legs, knees and ankles and by measuring the distance between the inner ankle bones. The condition is considered more severe the wider the distance between the ankles.

The doctor’s exam for diagnosing knock knees may include:

  • measurements of your child’s length and height 
  • measurements of weight and body mass index (BMI) 
  • measurements taken of knee extensions and rotations 
  • assessment of leg-lengths and leg symmetry 
  • observation and assessment of gait

What tests are needed?

If your child is within the normal age for knock knees, has a normal exam with a typical appearance and no functional problems, Boston Children’s doctors don’t usually take x-rays, preferring to avoid unnecessary radiation. If your child is older than the usual age range or if the legs aren’t symmetrical, your doctor will usually opt for standing x-rays.

What are the treatment options for knock knees?

Doctors treat most children who have knock knees with close observation during those years when this condition is a natural part of a child's leg development (typically ages 2 to 5), since the condition usually corrects itself with time. As a child grows, walking patterns become normal or near-normal by 7 to 8 years of age (or occasionally by the time the child becomes a teen).

Non-surgical options for knock knees

In a very few cases, the valgus may be severe and may not self-correct. Splints and other devices aren’t usually needed for a child at a natural stage of valgus up to age 7. These devices can be useful if the child’s natural valgus doesn’t straighten out on its own by about the time your child is 7 or 8 years old — or if the valgus has an underlying systemic or metabolic condition causing it.

For children with severe, unresolved knock knees, doctors may recommend:

  • a night brace, particularly if a family history of knock knees exists; the brace attaches to a shoe and works by pulling the knee up into a straight position
  • orthopedic shoes, usually equipped with a heel wedge and occasionally an arch pad

Surgical options for knock knees

In the rare event that natural growth, braces or shoes don't correct your child's knock knees, your doctor may recommend surgery. The surgery may involve either influencing bone growth (called a “guided growth” procedure) or cutting and straightening the thigh bone or shin bone (osteotomy of the femur or tibia).

Guided growth surgery means stopping the growth on the bent side of the bone (for knock knees, the inside of the knee). This is often done by implanting small metal devices that tether the medial/inside part of the growth centers around the knee, allowing the lateral/outer part to grow and straighten the knee.

Children usually have guided-growth surgery when they're approaching puberty (approximately age 11 in girls and 13 in boys). This allows time for the child's bones to continue to straighten on their own during the remaining growing years. This is a minimal day-surgery procedure with immediate weight bearing and a rapid return to sports allowed.

Osteotomy surgery is needed for more severe deformities or after growth is finished. After surgery, your child will probably stay in the hospital for a couple of days and be given pain medication. When your child goes home, limit weight-bearing activities. Crutches or a walker may be needed for a six to eight weeks. Physical therapy will help restore muscle strength. Typically, after six months, full activities, including sports may be resumed.

What is the long-term outlook for knock knees?

Since knock knees are self-correcting in up to 99 percent of cases, the long-term outlook is very positive for most children with the condition. For children who need surgery for severe forms of the condition, the outlook is also excellent. The procedures are quite safe — and children's bones usually heal faster and more reliably than adults. For children with surgically-repaired knock knees caused by an underlying condition (pathologic valgus), adulthood can bring can risks of arthritis, meniscal tears, pain, or dislocation.