Bow Legs and Knock Knees

Although infants are born with bowlegs, where the knees appear to "bow" out from the body, the knees tend to straighten out between 18 and 24 months of age. This means that when most children begin to walk, at around 12 months of age, they appear to be bow-legged.

Knock-knees, on the other hand, are when the knees appear to bend toward each other. If a child is knock-kneed, it will be most evident when he or she is around 3 years of age, and will then gradually become less pronounced. By age 7, these children will have attained the normal adult amount of slight knock-knee — 5 to 9 degrees — which they will maintain throughout their lives.

Although you may be concerned about the shape of your child's legs, a slight degree of bowing or knocking is normal. That said, if your child has severe knock-knees or bowlegs, it's a good idea for a pediatric orthopedist to take a look.

Again, a slight degree of bowing or knocking is normal. But if your child exhibits any of the following, it is probably a good idea to visit a pediatric orthopedist:

  • Excessive knee angle either inward or outward.
  • Unequal knee angles. While slight variation from one side of the body to the other is normal, a large difference between one leg and the other should be investigated.
  • Pain or other complaint connected to the knee angle.
  • Bowlegs after 3 years of age. This is when children have the greatest amount of knock-knee alignment and, therefore, bowlegs would be abnormal at this time.
  • Knock-knees at an angle greater than 15 degrees.

The main way doctors diagnosis bow legs or knock knees is through physical exam. In addition, X-rays may be taken when needed to get more information about the knee joint.

Surgery is the only way to change the knee angle — braces, shoe inserts and physical therapy are ineffective. Since normal leg development goes from bowlegs to knock-knees, surgery should be postponed until the child is at least 10 years old.

Two bones meet at the knee joint: the femur (thighbone) and the tibia (shinbone). Surgical treatment depends upon the maturity of the child. In younger children, whose growth plates are open and still growing, knee alignment can be changed by tethering the growth plates of the femur or tibia using staples. As the growth plate grows on the untethered side, the knee will grow out of its excessive angle.

In older children, who no longer have open growth plates, treatment consists of cutting, straightening and then holding the bones of the knee in place while they heal with metal implants, including pins, plates and screws.

Although both treatments have high success rates, they should be done only if clearly necessary and at the appropriate age.

Learn More

UCSF Research & Clinical Trials

 

Reviewed by health care specialists at UCSF Benioff Children's Hospital.

Related Information

UCSF Clinics & Centers

Orthopedics

Orthopedic Clinic
400 Parnassus Ave., Second floor
San Francisco, CA 94143
Phone: (415) 353-2967
Fax: (415) 353-2299
Appointment information

Related Conditions