Bow-Legs and Knock-Knees – Advice for Referrers

Usually no.  There is a very famous study from Scandinavia in 1975 which demonstrated the changing alignment of children’s leg as they age.  This is often remembered and shown in the Salenius Curve. 

The Salenius curve shows that all children are born with bow legs and that these are usually present until about the age of 2.  After this they become knock kneed.  The degree of knock-knee is most obvious between ages of 3-4.  The legs then gradually straighten reaching an adult shape by the age of 10-12.  This is often a very small degree of valgus.  Heavy children and children with loose ligaments stretch their knee joints and will appear to have greater deformity.  Many babies have big calf muscles, which can make the leg seem quite bent even the bones are only slightly curved. 

Symmetrical bow-legs before the age of two, and symmetrical knock-knees seen between the ages of 2 and 12 are termed “physiological” because these appearance are part of the normal growth and development.  It should be remembered that we are all slightly different in appearance and this goes for leg shape too.

Reasons for Referral therefore:

• Asymmetry
• Pain
• Progressive deformity out with that expected
• Concern regarding metabolic bone disease
• Bow legs > age 3
• Knock-knees worsening > age 10

For physiological symmetrical bow-legs and knock-knees, no.  It is helpful to explain the normal to the parents and it can be helpful to ask them to take photos 3 or 4 months apart which usually demonstrates to them that things are moving the way we would expect.

There is no place for physiotherapy, special shoes or braces as this is the normal development of lower limb alignment. 

Occasionally if there is an underlying cause this may require treatment.  This is indicated with the presence of asymmetric, pain, progressive deformity out with the normal curve.

Illustrations taken from:

https://www.narayanahealth.org/blog/knee-deformities-in-children-when-to-see-the-doctor/