Knock Knees

Overview

Knock knees — doctors call it genu valgum — is when a person stands with their knees touching or close together, but their ankles stay apart. It is a common pattern of leg growth. In most young children it is a normal stage of development and straightens on its own. In older children and adults, knock knees can be a sign of another problem, such as an injury, arthritis, or a growth condition.

Yes. Some degree of knock knees is very common in toddlers and young children. It is a normal part of how legs grow and straighten. Knock knees that continue past childhood, or that appear for the first time in an adult, are less common and need a doctor's check.

It mostly affects young children, especially between ages 2 and 5. It can also affect older children, teenagers, and adults. Adults may notice knock knees after a knee injury, with arthritis, or if they carry extra weight. Some people are born with leg shapes that run in the family.

Symptoms

Common symptoms

• Knees touch or almost touch when standing with feet together.
• A clear gap stays between the ankles while the knees are together.
• The legs may look slightly bent inward at the knees.
• The feet may point outward when walking.
• Some people walk with a stiff or awkward gait.
• Knee pain or aching after walking or standing for a long time.
• Legs feel tired after active play or exercise.
• Trouble running, jumping, or keeping up with other children.
• Shoes may wear unevenly on the inner side.

Symptoms in children

• Usually no pain at all — a parent or carer often notices the leg shape first.
• May trip or fall more often than other children of the same age.
• May complain of tired legs after playing.
• May sit with the knees turned inward and the feet apart (sometimes called W-sitting).
• Often affects both legs in a similar way.
• May walk with the feet turned out.

Symptoms in older adults

• Knee pain that gets worse with walking, stairs, or standing.
• Stiffness in the knees, especially in the morning or after rest.
• One knee may be more affected than the other.
• A feeling of instability, or the knee giving way.
• Difficulty walking long distances or keeping balance.
• Knock knees may develop slowly alongside knee arthritis.

Causes

Main causes

• Normal growth in young children — legs naturally turn slightly inward between ages 2 and 5, then straighten.
• Family history — some leg shapes run in families.
• Low vitamin D or calcium, which can soften growing bones (a condition called rickets).
• Injury to the knee or the growth plate in a child.
• Infection in the bone or joint.
• Rare bone growth conditions.
• Extra body weight, which puts more stress on the knees.
• Knee arthritis in adults, especially osteoarthritis.
• Previous fracture or surgery near the knee.
• Some genetic or skeletal conditions that affect how bones grow.

Risk factors

• Being between 2 and 5 years old — this is the normal age for knock knees.
• A family history of knock knees or bow legs.
• Being overweight or obese, at any age.
• Low vitamin D or calcium in the diet, or little sun exposure.
• A previous knee injury or infection.
• Joint problems such as arthritis in adults.
• Some medical conditions that affect bone growth.

When to see a doctor

See a doctor urgently if:

• Your child suddenly cannot walk or refuses to stand.
• There is severe knee pain, swelling, or a fever.
• One leg looks very different from the other, or changes quickly.
• There is numbness, weakness, or a cold, pale foot.
• A knee locks or gives way and you cannot straighten it.

Book a routine appointment if:

• Knock knees are still clearly present after age 7 or 8.
• Only one leg is affected, or one side is much worse.
• Your child has pain, a limp, or trouble keeping up with friends.
• You are worried about how your child walks or grows.
• An adult develops knock knees or notices knee pain and stiffness.
• There is a family history of leg shape problems or arthritis.

Diagnosis

A doctor will usually start by asking about your health, your child's growth, and any family history. They will watch you or your child stand and walk, and measure the gap between the ankles with the knees together. They will check the hips, knees, and ankles, and look at how the legs line up. For most young children, this simple exam is all that is needed.

Tests that may be done

• A physical exam and measurement of the ankle gap.
• Watching how you or your child walks (gait check).
• Growth charts to see if height and leg length are following a healthy pattern.
• X-rays of the legs or knees if the doctor wants to see the bones more clearly.
• Blood tests to check vitamin D, calcium, and other bone health markers.
• Rarely, other scans or a referral to a bone specialist if a growth condition is suspected.

What to expect at your appointment

The visit is usually quick and painless. Your doctor may ask you to stand and walk a few steps, and may measure your legs. Most children do not need X-rays or blood tests. If tests are needed, your doctor will explain why. You may be asked to come back in a few months to check how the legs are growing.

Treatment

Treatment depends on your age, the cause, and how much the knock knees affect daily life. Many young children need no treatment at all — just regular check-ups to make sure the legs are straightening as expected. If another condition is causing the knock knees, treating that condition is the first step. In older children and adults, treatment may include physiotherapy, shoe inserts, weight management, or in some cases surgery.

Self-care at home

• Keep active — walking, swimming, cycling, and play help keep leg muscles strong.
• Maintain a healthy weight to reduce strain on the knees.
• Wear comfortable, supportive shoes that fit well.
• Include calcium-rich foods such as milk, yogurt, cheese, leafy greens, and fortified foods.
• Ask your doctor or pharmacist about vitamin D if you think you may not get enough.
• Encourage your child to try different sitting positions — there is no strong evidence that W-sitting causes harm, but variety is good.
• Use a cushion or folded towel under the knees if sitting for long periods is uncomfortable.
• Follow any exercise plan given by a physiotherapist.

Medical treatments

Doctors may treat the underlying cause — for example, checking for and correcting low vitamin D or calcium, treating an infection, or managing arthritis. Some children benefit from physiotherapy to strengthen the muscles around the hips and knees. Shoe inserts (orthotics) or a brace may be suggested in some cases. For knee pain, your doctor or pharmacist can advise on general pain relief options that are safe for you. In adults, keeping the muscles strong and treating arthritis are important parts of care. Your doctor will tailor any plan to your age and needs.

When is surgery considered?

Surgery is not common. It may be considered if the knock knees are severe, cause a lot of pain, affect walking, are much worse on one side, or are caused by a growth problem. In children, a minor procedure can sometimes guide growth so the legs straighten. In adults, surgery may be an option if arthritis is severe. A specialist team would discuss the benefits and risks with you.

Living with this condition

Most children with knock knees live normal, active lives. You can keep an eye on how the legs look every few months and mention any changes at routine check-ups. For adults, staying active, keeping a healthy weight, and pacing activities can help reduce knee pain. If pain affects daily tasks, ask your doctor or physiotherapist for advice on ways to move more comfortably.

Lifestyle tips

• Stay physically active in ways you enjoy.
• Choose supportive shoes for walking and exercise.
• Take breaks from standing or walking if the knees ache.
• Keep a healthy weight through balanced meals and regular movement.
• Avoid smoking — it is bad for bone and joint health.
• Make sure children get plenty of outdoor play and a balanced diet.
• Attend routine child health checks so leg growth can be watched.

Diet and exercise

A balanced diet with enough calcium and vitamin D supports strong bones. Good sources of calcium include milk, yogurt, cheese, leafy greens, and fortified plant milks. Vitamin D comes mainly from sunlight and some foods, and a doctor or pharmacist can advise if a supplement is needed. For exercise, low-impact activities such as swimming, cycling, and walking are gentle on the knees. Strength exercises for the hips, thighs, and core can help support the knees. A physiotherapist can suggest safe exercises for your age and ability.

Mental health and emotional wellbeing

Children may feel self-conscious about how their legs look, and adults may worry about pain or mobility. These feelings are normal. Talk to your child's teacher or school if teasing is an issue. If you or your child feel anxious, low, or overwhelmed, speak to a doctor or a trusted adult. If you ever feel in crisis or unsafe, contact your local emergency number or a local crisis support service right away — you deserve help and support.

Prevention

The normal knock knees of young children cannot be prevented — they are part of healthy growth. Some other causes can be lowered in risk by keeping a healthy weight, eating a balanced diet with enough calcium and vitamin D, staying active, and getting injuries checked early. If you have a family history of leg shape problems, mention it to your doctor.

Screening programmes

There is no routine screening for knock knees. Leg alignment is usually checked at normal child health and school health checks. Adults with knee pain or a change in leg shape should ask their doctor for a check.

Complications

If left untreated

• Ongoing knee pain that limits walking, play, or exercise.
• Early wear and tear of the knee joint (osteoarthritis) in some people.
• A limp or changes in how you walk.
• Balance problems and a higher chance of falls in older adults.
• Uneven shoe wear and discomfort in the feet or ankles.
• Back or hip strain from changed walking patterns.
• In children, rarely, a growth problem that needs specialist care.
• Worry or low confidence about how the legs look.

Long-term outlook

The outlook is very good for most people. The great majority of young children with knock knees straighten out naturally by about age 7 or 8 without any treatment. Children who need help usually do well with simple care, physiotherapy, or, in rare cases, surgery. Adults with knock knees can often manage symptoms with healthy lifestyle habits and advice from their doctor. If you have concerns, regular check-ups can help catch any problems early.

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