Knock-knee describes an abnormal curvature of the legs causing the knees to touch or nearly touch even when the feet are apart.
Knock-knee is also called genu valgum and may be caused by bone structure problems or from other abnormalities.
A child may inherit knock knee and be born with it, or it may develop gradually over time because of skeletal deformities or diseases affecting the bones or joints, including scurvy (due to deficiency of vitamin C) and rickets (often due to deficiency of vitamin D).
Adults can develop knock knee after an injury or due to osteoarthritis or rheumatoid arthritis affecting their joints.
Knock-knee can cause difficulty walking and pain from the muscle and bone strain it can cause.
Knock knee may be treated by remedying an underlying medical condition, such as rickets, or by a brace or orthopaedic shoes. Occasionally it requires surgery. This may mean inserting small pieces of metal to guide knee growth in children, or an operation called an osteotomy to realign the femur leg bone.
Knock knee will not usually be diagnosed in a child until they are around 6-7 years old. Babies have a natural tendency to be bow-legged until they are about 3 years old, a result of having their legs folded in the womb. Most 4 to 5 year olds then become a little knock-kneed, but this usually disappears at around age 6-7. However, parents who are concerned, especially if the gap between the child's ankles is wider than around 10cm or the child is in pain, should seek medical advice.