What causes knock knees

What are Knock Knees (Genu Valgum)?

Knock knees, or genu valgum, is a condition where the knees angle inward and touch or almost touch when a person stands with their feet and legs straight. When the person stands, there is a significant gap between their ankles. This condition is more common in children and often resolves naturally as they grow and develop. However, in some cases, it can persist into adulthood or develop later in life, indicating a potential underlying issue.

Causes of Knock Knees

In Children:

The most common cause of knock knees in children is related to their natural growth and development. As babies, many have bow legs (genu varum), where the legs curve outward. This typically corrects itself as they grow, and in the process, many children go through a phase of knock knees before their legs straighten properly. This developmental phase usually occurs between the ages of 3 and 6 years old and most often resolves on its own by the age of 7 or 8.

Several factors can influence or exacerbate knock knees in children:

• Rapid Growth: The uneven growth of the bones in the legs and pelvis can temporarily cause the knees to angle inward.
• Obesity: Being overweight puts extra stress on the joints, including the knees, which can worsen the inward angulation.
• Flat Feet (Pes Planus): Some research suggests a link between flat feet and knock knees, possibly due to biomechanical changes in the way the foot and ankle function.
• Genetics: A family history of knock knees might increase a child's likelihood of developing the condition.

In Adults and Older Children:

While many cases of knock knees in children resolve naturally, persistent or adult-onset genu valgum usually points to an underlying medical condition or injury. These can include:

• Arthritis: Osteoarthritis, particularly in the knee joint, can lead to the breakdown of cartilage and bone, causing the knee to collapse inward. Rheumatoid arthritis can also affect the knee alignment.
• Osteochondritis Dissecans: This condition involves a piece of bone and cartilage becoming loose within the joint, which can affect knee stability and alignment.
• Rickets: A condition caused by vitamin D deficiency, rickets softens bones and can lead to deformities like knock knees, especially in children with severe deficiency.
• Bone Fractures: Fractures in the femur (thigh bone) or tibia (shin bone) near the knee joint, if not healed properly, can result in malunion and altered knee alignment.
• Bone Infections (Osteomyelitis): Infections can damage bone and affect its growth and structure, potentially leading to deformities.
• Neuromuscular Conditions: Conditions affecting the nerves and muscles, such as cerebral palsy or polio, can impact muscle tone and control around the knee, leading to abnormal alignment.
• Tumors: Although rare, bone tumors in or near the knee can cause structural changes leading to knock knees.
• Previous Surgery: Certain surgical procedures on the knee or leg can sometimes alter the joint's mechanics and alignment.

When to See a Doctor

For most children, knock knees are a normal part of development and do not require treatment. However, it is advisable to consult a doctor if:

• The knock knees are severe or noticeable when the child is not bearing weight.
• The condition does not improve or worsens between the ages of 7 and 8.
• Only one leg is affected.
• The child experiences pain in the knees, hips, or legs.
• The child trips or falls frequently.
• There are other signs of developmental issues or medical conditions.

In adults, any new onset or worsening of knock knees should be evaluated by a healthcare professional to rule out underlying diseases or injuries.

Diagnosis and Treatment

A doctor will typically diagnose knock knees through a physical examination, observing the alignment of the legs while the patient stands and walks. X-rays may be used to assess the degree of angulation and check for any signs of arthritis, bone abnormalities, or other underlying issues. Blood tests might be ordered if conditions like rickets are suspected.

Treatment varies depending on the cause and severity:

• Observation: For most children, especially those with mild to moderate knock knees during the typical developmental phase, observation is sufficient.
• Weight Management: Encouraging a healthy weight is crucial for both children and adults, as excess weight strains the knee joints.
• Orthotics: Shoe inserts or orthotic devices may help manage associated flat feet and improve biomechanics.
• Physical Therapy: Exercises to strengthen muscles around the knee and improve flexibility can be beneficial.
• Bracing: In some cases, especially if the condition persists or is severe, special braces might be recommended to guide bone growth or improve alignment.
• Surgery: Surgical intervention is usually reserved for severe cases, persistent knock knees in older children or adults, or when caused by significant underlying conditions. Procedures like osteotomy (cutting and realigning the bone) or guided growth surgery (using plates or screws to alter bone growth) may be performed.

The prognosis for knock knees is generally good, especially when it resolves naturally in childhood. Early diagnosis and appropriate management of underlying causes are key to preventing long-term complications such as arthritis or chronic pain.