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Causes of Knock knee

Knock-knee is fairly normal in healthy children under the age of six and should not cause any concern. It occurs because the weight falls to the outside of the knee joint.

At the age of three, over 20 per cent of children have at least a five cm gap between their ankles, but by the age of seven, only about one per cent of children do. In most cases the knock knee corrects itself as the child grows: the legs gradually change shape and become straight.

If the distance between the ankles is greater than 10cm or the knees are asymmetrical the child may have an underlying medical condition, such as a growth problem or a disease.

Childhood diseases that can cause knock knee are rickets, scurvy and Blount’s disease. Rickets is caused by a vitamin D deficiency; bone development is softer than normal and the legs start to bow. Rickets is no longer common in the UK and does not occur in children who have a healthy diet. Blount’s disease is when the lower legs do not grow properly and the legs start to bow.

Family history of skeletal abnormality may also be a factor. Conditions such as an uncorrected fracture of the shin bone, rheumatoid arthritis, osteoarthritis or Paget’s disease can distort the ends of the bones and cause knock knee in adults.

• Kawasaki diseaseKetosisKidney failureKidney infectionKidney stonesKidney transplantKnee replacementKnock kneeKyphosis

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