Knock Knees (Genu Valgum): Causes, Biomechanics, and Management Strategies

How Do You Get Knock Knees?

Knock knees, clinically known as genu valgum, typically develop due to a combination of genetic predisposition, developmental growth patterns, metabolic conditions, and acquired factors such as muscle imbalances, joint injuries, and excessive biomechanical stress.

Understanding Genu Valgum: What Are "Knock Knees"?

Genu valgum, commonly referred to as "knock knees," is a lower limb alignment deviation where the knees angle inward, touching or nearly touching, while the ankles remain separated when standing with feet together. In a healthy alignment, the hip, knee, and ankle joints form a relatively straight line, ensuring even distribution of weight and stress through the lower kinetic chain. Genu valgum disrupts this alignment, placing abnormal forces on the knee joint and surrounding structures.

Primary Causes of Knock Knees (Genu Valgum)

The development of knock knees can stem from a variety of factors, ranging from congenital conditions to lifestyle influences. Understanding these causes is crucial for both prevention and effective management.

• Developmental and Growth Factors:
  • Physiological Genu Valgum in Childhood: It is common and often normal for children between the ages of 2 and 6 to exhibit mild genu valgum. This is typically a transient phase as part of normal growth and development, and most children naturally outgrow it by age 7 or 8.
  • Growth Plate Anomalies: Issues with the epiphyseal plates (growth plates) in the femur or tibia can lead to uneven growth, resulting in valgus deformity. This can be due to injury, infection, or genetic conditions.
• Genetic Predisposition: A family history of genu valgum can increase an individual's likelihood of developing the condition, suggesting a genetic component influencing bone and joint development.
• Metabolic and Nutritional Deficiencies:
  • Rickets: This bone-softening disease, most commonly caused by prolonged severe vitamin D deficiency, leads to weakened bones that can bend under the body's weight, contributing to genu valgum in children.
  • Renal Osteodystrophy: Kidney disease can impair the body's ability to maintain proper bone health, leading to skeletal deformities.
• Trauma and Injury:
  • Fractures: Healing fractures around the knee joint, particularly those involving the growth plates in children or resulting in malunion, can alter the anatomical alignment and lead to genu valgum.
  • Ligamentous Injuries: Chronic instability or laxity in the knee ligaments (e.g., medial collateral ligament, anterior cruciate ligament) can contribute to valgus collapse, though this is less common as a primary cause.
• Overuse and Biomechanical Stress:
  • Repetitive Valgus Loading: Certain sports or activities that involve repetitive knee valgus (e.g., deep squats with poor form, skiing, certain types of jumping) can, over time, contribute to soft tissue adaptations and bone remodeling that encourage a knock-kneed alignment.
  • Joint Degeneration (Arthritis): Osteoarthritis, particularly in the lateral compartment of the knee, can lead to cartilage loss and bone changes that shift the joint alignment into valgus.
• Obesity: Excessive body weight places increased mechanical stress on the knee joints. Over time, this chronic load can contribute to the progressive development or worsening of genu valgum, especially when combined with other predisposing factors.
• Muscle Imbalances and Weakness:
  • Weak Hip Abductors and External Rotators: Muscles like the gluteus medius and gluteus maximus are crucial for stabilizing the pelvis and preventing inward collapse of the femur (thigh bone). Weakness in these muscles can lead to hip adduction and internal rotation, which translates to a valgus stress at the knee.
  • Tight Hip Adductors and Internal Rotators: Overly tight muscles on the inner thigh (adductors) and hip internal rotators can pull the femur inward, contributing to a knock-kneed posture.
  • Weak Vastus Medialis Obliquus (VMO): The VMO, a part of the quadriceps, helps stabilize the kneecap and prevent its lateral tracking. Imbalance or weakness here can contribute to patellofemoral issues often seen with genu valgum.
  • Foot Pronation: Excessive or prolonged pronation (flattening) of the arches of the feet can internally rotate the tibia (shin bone), which in turn contributes to a valgus stress at the knee joint, affecting the entire kinetic chain.

The Biomechanics of Genu Valgum: How It Affects the Body

Genu valgum significantly alters the biomechanics of the lower limb, leading to various compensatory movements and potential issues:

• Increased Stress on Lateral Knee Compartment: The inward angle of the knees shifts weight-bearing forces primarily to the lateral (outer) side of the knee joint, increasing the risk of lateral meniscus tears and cartilage degeneration.
• Patellofemoral Pain Syndrome: The altered alignment can cause the kneecap (patella) to track improperly, leading to pain and irritation behind or around the kneecap.
• Altered Gait Pattern: Individuals with knock knees may develop an altered walking pattern (gait) to compensate for the misalignment, which can place undue stress on other joints like the hips and ankles.
• Increased Risk of Injury: The compromised alignment can make the knee more susceptible to injuries, especially during dynamic movements, due to altered muscle activation patterns and joint loading.
• Associated Hip and Ankle Issues: Compensatory mechanisms can lead to internal rotation of the hips and increased pronation of the feet, potentially causing pain or dysfunction in these areas over time.

Recognizing Knock Knees: When to Seek Professional Advice

While mild genu valgum in young children is often normal, persistent or progressive knock knees, especially when accompanied by pain, functional limitations, or asymmetry, warrant professional evaluation. A healthcare professional, such as an orthopedic surgeon, physical therapist, or kinesiologist, can accurately diagnose the underlying cause and recommend appropriate interventions. Early intervention can often prevent the progression of the deformity and mitigate associated complications.

Management and Correction Strategies

Management strategies for genu valgum depend on its cause, severity, and the individual's age.

• Non-Surgical Interventions:
  • Physical Therapy: Targeted exercises to strengthen weak muscles (e.g., hip abductors, glutes, VMO) and stretch tight ones (e.g., hip adductors, hamstrings) can improve alignment and reduce symptoms. Gait training and neuromuscular re-education are also crucial.
  • Orthotics: Custom foot orthotics can help address excessive foot pronation, which may contribute to genu valgum.
  • Weight Management: For individuals with obesity, weight reduction can significantly decrease the load on the knee joints and improve alignment.
  • Bracing: In some pediatric cases, bracing may be used to guide bone growth.
• Surgical Interventions: For severe cases, or when non-surgical methods fail, surgical options like an osteotomy (reshaping the bone) may be considered, particularly in adolescents with significant growth remaining or adults with advanced degeneration.