Knock Knees (Genu Valgum): Children and Adults

Quick answer

Knock knees are normal between about 3 and 7 years and usually straighten on their own

Babies are born with bowed legs. As children start walking, the legs straighten and then usually move into a knock-kneed position, which is most noticeable around 3 to 4 years of age. Most children reach the adult alignment, with a slight inward angle, by about 7 or 8 years. No braces or special shoes are needed for this normal pattern. Knock knees should be checked if they are severe, getting worse after age 7, affect one leg much more than the other, cause pain or limping, or come with short stature. In adults, knock knees can result from arthritis of the outer part of the knee, an old injury, or bone conditions. Exercises do not change bone shape, but they improve how the knee is controlled during movement.

What knock knees are

When a person with knock knees stands with their knees together, there is a gap between the ankles. Doctors measure this gap (the intermalleolar distance) and the angle between the thigh and shin bones to decide whether the alignment is within the normal range for age.

It is important to separate structural knock knees, where the bones are angled, from dynamic knee valgus, where the knees fall inwards only during movements such as squatting, landing or running. Dynamic valgus is common in people with weak hip muscles and is linked to knee pain such as runner’s knee.

Normal development in children

Birth to 18 months: legs are naturally bowed.
Around 18 to 24 months: the legs become straight.
3 to 4 years: knock knees are most pronounced, sometimes with an ankle gap of several centimetres.
By 7 to 8 years: most children have reached the adult alignment.

Flat feet often appear together with knock knees in young children and usually improve as well; see flat feet exercises.

Causes of abnormal knock knees

Persistent or severe knock knees after age 7 without another cause (idiopathic).
Excess body weight, which loads the inside of the knee.
Rickets from low vitamin D or calcium, or other bone and kidney conditions.
An injury or infection affecting the growth plate, usually on one side only.
Genetic or skeletal conditions, often with short stature.
In adults: arthritis of the outer part of the knee, rheumatoid arthritis, or old fractures.

Knock knees vs bow legs

Bow legs (genu varum) are the opposite: the knees stay apart when the ankles touch. Bow legs are normal in babies and toddlers, while knock knees are normal in preschool children. In adults, bow legs are often linked to wear of the inner part of the knee, and knock knees to wear of the outer part.

In both cases the questions are the same: is it within the normal range for age, is it symmetrical, and is it improving with time?

Knock knees in adults

Mild knock knees in adults are common and often cause no problems. When the angle is larger, more load passes through the outer side of the knee, which can contribute to arthritis there over the years, and the kneecap may track less well, causing pain at the front of the knee.

Adults with knee pain and knock knees benefit from strengthening, weight management when relevant and appropriate footwear. Surgery is reserved for severe deformity with pain and arthritis; see knee replacement recovery.

Exercises that help knee control

Clamshells: lying on your side with knees bent, lift the top knee while keeping the feet together.
Side-lying leg raises: strengthen the hip abductors that stop the knee falling inwards.
Glute bridges: lift the hips from the floor, keeping the knees in line with the feet.
Mini squats with a band: a resistance band around the knees reminds you to push them out slightly.
Step-downs: step down slowly from a low step, keeping the knee over the second toe.
Balance work: standing on one leg improves ankle, knee and hip control.

These exercises do not straighten the bones, but they reduce dynamic valgus and can ease knee pain. See also hip mobility exercises.

Medical treatment options

Observation: for normal knock knees in young children, with a check over time.
Treating the cause: for example vitamin D and calcium in rickets.
Guided growth: in children with persistent severe knock knees, a small operation slows growth on the inner side of the growth plate so the leg straightens as the child grows.
Osteotomy: in adolescents and adults, the bone is cut and realigned.
Knee replacement: in adults with severe arthritis and deformity.

Braces, insoles and special shoes do not correct normal childhood knock knees.

When to see a specialist

Knock knees that are severe or getting worse after age 7.
Only one leg is affected, or one is much worse than the other.
Pain, limping or difficulty running and keeping up with other children.
The child is much shorter than expected for their age.
Adults with knee pain, swelling or giving way.

Key points to remember

Knock knees are normal in children aged about 3 to 7 and usually correct naturally.
Persistent, one-sided or painful knock knees need assessment.
Strengthening the hips improves knee control in children and adults.
Surgery is only needed for severe or progressive cases.

Questions about knock knees

These answers are general information and do not replace an examination or individual medical advice.

At what age do knock knees go away?

Most children reach the adult alignment by about 7 or 8 years.

Can knock knees be corrected in adults?

Exercises improve control and pain but not the bone shape. Significant deformity can only be corrected surgically.

Do knock knees cause knee pain?

Mild knock knees often cause no pain. Larger angles can contribute to pain at the front or outer side of the knee.

Can flat feet cause knock knees?

Flat feet and knock knees often appear together, and the rolling in of the foot can make the knee fall inwards during movement.

Is knock knees a disability?

No. Most people with knock knees have no limitations. Only severe cases affect walking or cause pain.

Do braces help knock knees?

Braces do not correct normal childhood knock knees and are rarely used.

Sources

This guide is for general information and does not replace medical advice. How a problem is diagnosed and treated depends on your examination and medical history. If you think you have an emergency, contact your local emergency services.