knock knee

Last reviewed 06/2020

Genu valgum is frequently seen between the ages of 2 and 4 years. The condition is usually benign if symmetrical and independent of any other abnormality.

  • common and often associated with in-toeing (maximal at approx. 4 years); most resolve by 7 years (1)

The degree of genu valgum is assessed by measuring the inter-malleolar gap. This is the distance between the two malleoli when the knees are gently touching with the legs in adduction. An inter-malleolar gap of 4 inches (or less) at 4 years-of-age normally will correct with growth.

If the condition is severe and progressive then rickets or scurvy must be considered.

In the UK, rickets is most commonly seen in immigrant Asian children. Radiographic appearance is diagnostic, showing the typical frayed metaphyseal changes. Serum alkaline phosphatase is usually raised.

In the older patient genu valgum may occur in association with rheumatoid arthritis or osteoarthritis. Genu valgum may present secondary to uncorrected fractures of the lateral tibial table and after a variety of paralytic neurological disorders.

A permanent deformity may be amenable to osteotomy.


  • (1) ARC. Sports-Related Musculoskeletal Disorders. Reports on the Rheumatic Diseases 2008;14.