Knock Knees (Genu valgum): Symptoms, Causes & Treatment

Written by: Editorial Team

Medically reviewed by: Dr. Raghuram - Orthopaedic Consultant, Trauma, Shoulder and Knee Arthroscopic Surgeon, Hip and Knee Joint Replacement Specialist

Overview | Epidemiology | Types | Symptoms | Causes and Risk Factors | Complications | Diagnosis | Treatment | Prevention | Knock knees vs Normal knees | Genu valgum vs Varum | FAQs | When to consult a Doctor

Knock knees (Genu valgum) definition

 Knock knees deformity (genu valgus, valgus knee, or Genu valgum) is a condition in which the knees angle inward and touch each other while the ankles remain apart when standing. It is commonly seen during normal growth in children, but may become a concern if it continues or gets worse. Symptoms generally include visible knee misalignment, knee pain, difficulty in walking, and an abnormal gait pattern.

This condition can be a normal part of growing up in children, or it may happen due to issues like vitamin D deficiency (rickets), obesity, inherited bone problems, or past injuries to the growth plate. Poor nutrition, being overweight, or a history of bone injuries can also increase the risk. If left untreated or if the condition worsens, knock knees can lead to several complications, including knee pain, altered gait, joint damage, difficulty in physical activities, and postural problems.

Diagnosis is done through a clinical evaluation and imaging tests to check the alignment and severity of the limbs. Treatment depends on the cause and how severe it is, ranging from observation and physiotherapy to bracing or surgery in severe cases. Treatment is typically provided by orthopedic specialists, particularly pediatric orthopedic surgeons, and physiotherapists.

Genu valgum, or knock knees, is common in young children, particularly between the ages of 3 and 4, and usually go away by age 7. Around 7.1% of schoolchildren experience it, with higher rates in obese children. In adults, around 10% of people, especially those who are overweight, have knock knees. The condition is often part of normal childhood development. New cases in adults usually happen because of factors like obesity, joint damage, or injury.

In India, genu valgum (knock knees) is common in children under 7, with knee angles peaking around age 6 and typically improving by age 10. However, pathological genu valgum affects about 10-11% of school-aged children, especially in rural areas. Contributing factors include fluorosis, obesity, and nutritional deficiencies like rickets. Children with high body mass index (BMI), family history, or those living in areas with fluoride exposure are at high risk. While mild genu valgum is normal, persistent or severe cases may require medical attention.

Knock knees, or genu valgum, are broadly classified to help distinguish a normal stage of childhood growth from forms caused by disease or structural problems. The most accepted classification is into physiological and pathological genu valgum, with further clinical description based on cause, side involved, and severity.

Classification of Types of Knock Knees (Genu Valgum)

Based on Developmental Nature

• Physiological Genu Valgum 
• Pathological Genu Valgum

Types of Pathological Genu Valgum

• Metabolic or Nutritional Genu Valgum 
• Post-Traumatic Genu Valgum 
• Dysplastic or Congenital Genu Valgum 
• Idiopathic Genu Valgum 
• Obesity-Associated Genu Valgum 

Additional Clinical Classification

• Based on Laterality
• Bilateral Genu Valgum 
• Unilateral Genu Valgum
• Based on Severity
• Mild Genu Valgum 
• Moderate Genu Valgum 
• Severe Genu Valgum
  

Physiological genu valgum: This is the normal developmental type seen in children. It usually appears after the age of about 2 years, becomes most noticeable around 3 to 4 years, and gradually improves to near-normal alignment by around 7 years. It is usually bilateral, symmetrical, painless, and self-correcting, so it generally does not need treatment unless it is severe, progressive, or persists beyond the expected age. 

Pathological genu valgum: This is the abnormal type of knock knees. It is suspected that the deformity is severe, worsening, asymmetric, painful, associated with gait problems, or persists after about 7 years of age. Unlike physiological genu valgum, this form is usually related to an underlying disorder and may need medical or surgical treatment. 

Metabolic or nutritional genu valgum: This type usually develops due to disorders that affect bone mineralization and growth, especially rickets or vitamin D deficiency. Because the bones are softer and weaker, the knees may gradually angle inward under body weight.

Post-traumatic genu valgum: This occurs after an injury near the knee, especially when the growth plate is affected. Uneven growth after the injury can lead to progressive inward angulation of one or both knees. 

Dysplastic or congenital genu valgum: This type is associated with skeletal dysplasia or congenital bone-growth abnormalities. It is less likely to correct on its own and often requires orthopaedic care because the bone structure itself is abnormal.

Idiopathic genu valgum: In this type, genu valgum persists, but no definite underlying disease is identified. It is considered a diagnosis after excluding more obvious causes such as rickets, trauma, or skeletal disorders.

Obesity-associated genu valgum: Genu valgum is related to obesity, particularly in children and adolescents. Excess body weight increases mechanical loading across the knee joint, which can accentuate the valgus alignment and contribute to the persistence or progression of the deformity.

Based on Laterality

• Bilateral Genu Valgum: This refers to knock knees affecting both legs. It is more commonly seen in physiological (normal developmental) cases and some metabolic conditions. The deformity is usually symmetrical and less concerning if it follows the normal growth pattern in children.

• Unilateral Genu Valgum: Unilateral deformity involves just one leg and is uncommon. It often points to underlying problems such as past injury, growth plate issues, infection, or bone conditions. Because it's more likely pathological, it needs careful evaluation.

Based on Severity

• Mild Genu Valgum: In mild cases, the inward angulation of the knees is minimal. There is usually no impact on walking, function, or daily activities. It is often observed in growing children and may not require treatment.

• Moderate Genu Valgum: At this stage, the knees bend inward more noticeably, which may affect walking or cause mild discomfort. It is important to monitor the condition closely, and in some cases, non-surgical treatment may be suggested.

• Severe Genu Valgum: Severe cases involve marked inward angulation of the knees, which often lead to functional problems like difficulty walking, joint strain, or cosmetic concerns. It may also increase the risk of chronic (long-term) joint issues, and medical or surgical intervention is usually considered.

Most individuals with genu valgum may not experience symptoms or functional limitations. However, in more severe cases, the condition can lead to pain, difficulty walking, and joint instability, which can affect mobility and daily activities. Genu valgum symptoms include the following:

• Visible knee misalignment 
• Knee pain 
• Abnormal gait 
• Joint instability 
• Fatigue and discomfort in lower limbs 
• Hip, ankle, or foot pain 
• Early osteoarthritis (OA) risk 
• Flat feet or foot rotation 
• Emotional concerns 

Visible knee misalignment: The primary symptom of genu valgum is the inward angulation of the knees, where the knees touch while the ankles remain apart, often more than 8 cm.

Knee pain: Individuals with genu valgum may experience discomfort or pain in the knees, particularly during activities such as walking, running, or standing for long periods. The pain is caused by abnormal stress on the knee joints due to misalignment, and it tends to worsen with physical activity.

Abnormal gait: This knock knee syndrome is caused by an altered walking pattern. This can include a limp, waddling, or difficulty walking in a straight line due to the knee misalignment.

Joint instability: In severe cases, knees may feel weak or unstable, especially on stairs or long walks. This raises the risk of falls and injuries.

Fatigue and discomfort in the lower limbs: Standing or walking for a long time can make the legs tired or sore. The misaligned knees put extra stress on the legs, making it harder to keep going.

Hip, ankle, or foot pain: The misalignment of the knees can cause uneven distribution of the body's weight, leading to pain in the hips, ankles, or feet over time. This is because the altered mechanics place additional strain on these joints.

Early osteoarthritis (OA) risk: Persistent genu valgum, especially in adults, can lead to increased stress on the knee cartilage, which raises the risk of early osteoarthritis. Over time, the misalignment can contribute to the degeneration of knee joints.

Flat feet or foot rotation: Knock knees can contribute to flat feet (pes planus) or outward rotation of the feet. As the knees are misaligned, the body compensates by changing the mechanics of the feet, which can lead to further discomfort.

Emotional concerns: Knock knee deformity, due to its visible nature, often leads to self-consciousness. Both children and adults may experience emotional distress because of the noticeable misalignment, which can affect self-esteem, social interactions, and overall quality of life. Parents of affected children may also worry about how the condition will progress.

Genu valgum (knock knees) can arise from natural growth patterns in children or from medical conditions affecting bone development. Certain factors can increase the likelihood of developing or worsening the condition. Understanding both the causes and contributing factors helps guide appropriate monitoring and treatment. The main causes and risk factors include: 

• Developmental Causes
• Nutritional Deficiencies (Rickets)
• Trauma or Injury
• Obesity
• Metabolic/Renal Disorders
• Skeletal Dysplasias/Congenital
• Infections
• Arthritis
• Tumors/Genetic Conditions

Developmental Causes: Genu valgum can be a normal part of childhood development, particularly in children between the ages of 2 and 5. During this growth phase, the alignment of the knees may appear bowed, but it typically corrects itself as the child matures.

Nutritional Deficiencies (Rickets): Vitamin D deficiency, often resulting in rickets, causes weakened bones that may result in misalignment. The condition impairs bone mineralization, leading to deformities like knock knees, especially in growing children.

Trauma or Injury: Injuries to the knee or growth plates in the leg can interfere with normal bone development. Trauma may result in permanent deformities like genu valgum if it disrupts bone growth or alignment.

Obesity: Excess body weight places additional stress on the legs, which can contribute to inward angling of the knees. In children, this increased load may lead to or worsen genu valgum due to the ongoing growth and development of the bones.

Metabolic/Renal Disorders: Metabolic conditions like renal osteodystrophy can make bones weak and affect their growth. Imbalances in calcium and phosphate can stop bones from developing normally, causing knees to turn inward.

Skeletal Dysplasias/Congenital: Skeletal dysplasias are a group of disorders that affect bone development and may result in abnormal bone growth. Congenital knock knees can occur due to underlying genetic conditions that affect skeletal growth and alignment.

Infections: Infections in bones or joints, such as osteomyelitis, can affect how bones grow. If the knees or nearby areas get infected during growth, the bones may grow crooked, causing the knees to angle inward.

Arthritis: Conditions like juvenile arthritis or rheumatoid arthritis can cause long-term inflammation in the knee joint. If the growth areas of the bones are affected, this can make the knees angle inward, resulting in genu valgum.

Tumors/Genetic Conditions: Tumors, whether non-cancerous or cancerous, that affect the bones or nearby tissues can disturb normal bone growth and lead to deformities. Additionally, genetic conditions that affect bone development can also increase the chances of developing this condition.

Frequently Asked Questions (FAQs) Knock Knees (Genu Valgum)

Genu valgum can be identified when, on standing with the legs straight, the knees touch while the ankles remain apart. This malalignment may be associated with discomfort or difficulty in walking. A proper orthopedic evaluation is required for accurate diagnosis, which may include physical examination and imaging studies to assess the severity of the condition.

In children, the early signs include the knees appearing closer together while standing, and there may be difficulty walking due to the altered gait. In adults, early signs often include knee pain, discomfort while walking, or difficulty maintaining balance. If untreated, symptoms may deteriorate, leading to joint degeneration.

Knock knees can occur in children, especially as they go through developmental stages. It is most common in children aged 2 to 4 years as a normal part of growth. Adults can also have it, particularly if they are obese (overweight), have joint problems, or certain inherited conditions. It is seen more often in women than men because of differences in bone structure.

Knock knees are normal in young children and usually appear between 2 to 4 years of age. In most cases, they improve naturally and go away by around 7 years as the child grows. However, if knock knees continue beyond this age or occur in adults, it may be a sign of underlying bone problems, medical conditions, or nutritional deficiencies, and a doctor’s evaluation is needed.

Yes, flat feet can contribute to knock knees. When the arches of the feet are flat, it affects the alignment of the lower body, causing extra stress on the knees. This misalignment can make the knees more likely to turn inward over time. The condition may worsen if not addressed, leading to further knee problems.

As people age, the wear and tear on the knees, combined with muscle weakening or imbalances, can lead to the development of genu valgum. Conditions like osteoarthritis can also cause structural changes in the knees, which may contribute to knock knees. Other factors, such as obesity or joint injury, may exacerbate the condition.

Yes, knock knees are prevalent among children, especially between the ages of 2 and 5. It is a normal part of the growth process, and most of the children outgrow it as they become older. In some cases, it persists throughout puberty or age, requiring medical care if severe.

Knock knees are generally not serious if they are physiologic and resolve naturally in childhood. However, if the problem persists into adulthood or is accompanied by pain, instability, or early arthritis, it can worsen.If left untreated, it may lead to joint degeneration or functional impairment.

Genu valgum (knock knees) in children often corrects naturally as they grow. It is a normal part of development in many kids, and the legs usually straighten out on their own by around 6–7 years of age without any treatment.

In adults, genu valgum usually does not improve on its own because bone growth has already stopped. Subtle (mild) cases may be managed with physiotherapy, strengthening exercises, and lifestyle changes, but more severe deformities may require surgical correction to realign the bones and improve function.

For knock knees, it is recommended to consult an orthopedic specialist. Children should be referred to a pediatric orthopedic surgeon, while adults should see an adult orthopedic surgeon. The severity of the condition will be assessed, and appropriate treatment options such as physiotherapy, braces, or surgery may be advised.

Physiotherapists treat genu valgum by focusing on strengthening and improving the flexibility of the muscles surrounding the knee joint. Physiotherapists may use techniques such as manual therapy, specific exercises to correct knee alignment, and posture training to help realign the knees and reduce pain.

The fastest treatment option for knock knees depends on the severity. In mild cases, physical therapy and exercises may help within a few months. For more severe cases, surgery (such as osteotomy or realignment of the bones) may be needed for quicker correction, but recovery times vary.

Yes, surgery is an option for severe cases of genu valgum, especially when it causes significant pain, instability, or dysfunction. Procedures like osteotomy (realigning the bones) are commonly used. In some cases, a total knee replacement may be required if arthritis has developed.

Obesity can contribute to the development or worsening of knock knees, especially in adults. Excess body weight places additional stress on the knee joints, which may exacerbate alignment issues. While obesity alone may not directly cause genu valgum, it can be a significant factor in aggravating the condition and contributing to joint degeneration.

Untreated genu valgum, particularly in adults, can lead to further joint damage, pain, and increased risk of developing osteoarthritis. Over time, misalignment of the knees can affect walking, which causes hip and lower back pain and reduces overall mobility. Early treatment helps prevent long-term complications.

Consult a doctor for knock knees if the condition persists beyond the age of 7 years, worsens over time, or causes pain or discomfort. Signs that need attention include:

• Difficulty walking or running 
• Knee pain or stiffness 
• Abnormal gait or limping 
• Worsening deformity or imbalance 
• Difficulty with daily activities due to knee misalignment 

If these symptoms continue, it is important to consult a knock knee specialist who can assess the severity of the condition and recommend the appropriate knock knee treatment. Early intervention can help prevent further complications and improve overall quality of life.