Knock Knees (Genu Valgum): Understanding Its Impact, Causes, and Management

Can knock knees decrease height?

While severe skeletal deformities can impact overall stature, typical genu valgum (knock knees) does not directly or significantly decrease a person's adult height, as it primarily involves an angular misalignment of the knee joint rather than a shortening of the long bones.

Understanding Genu Valgum (Knock Knees)

Genu valgum, commonly known as knock knees, is a lower limb alignment condition where the knees angle inward and touch or nearly touch when the legs are straightened, while the ankles remain separated. This creates an "X" shape with the legs. It is a common physiological variation in young children, often resolving naturally by age 6-8. However, in some individuals, it persists into adolescence or adulthood, or can develop later in life due to various factors.

The Biomechanics of Genu Valgum

From a biomechanical perspective, genu valgum represents an altered alignment of the kinetic chain involving the hip, knee, and ankle joints.

• Femoral Angle: The primary issue often lies in an excessive inward angle of the femur (thigh bone) relative to the tibia (shin bone) at the knee joint. This places the knee closer to the body's midline.
• Joint Stress: This altered alignment can redistribute forces across the knee joint, typically increasing compressive stress on the lateral (outer) compartment and tensile stress on the medial (inner) structures. It can also influence mechanics at the hip and ankle.
• Limb Length: While the angle of the bones is altered, the actual length of the femur and tibia themselves, which are the primary determinants of a person's height, remains unchanged. The bones are not shortened by the valgus alignment.

Does Genu Valgum Directly Reduce Stature?

The direct answer is no, typical genu valgum does not directly or significantly decrease a person's adult height.

• No Bone Shortening: The bones that contribute to height (femur, tibia) are not physically shortened due to the angular deviation seen in knock knees. Your maximum potential height, determined by the length of your long bones, remains unaffected.
• Perceived vs. Actual Height: While the inward angle of the knees might subtly alter the effective vertical alignment of the leg, this effect on overall adult height is negligible and not a measurable decrease in stature. A person with knock knees stands at the same height as they would if their knees were perfectly aligned, assuming no other underlying skeletal conditions.
• Severe Deformities: It is important to distinguish typical genu valgum from extremely rare, severe congenital skeletal dysplasias or metabolic bone diseases that can cause significant bone malformations and genuinely impact growth and final height. These are not what is typically referred to as "knock knees" in a general health and fitness context.

Potential Consequences and Concerns of Genu Valgum

While not directly impacting height, persistent genu valgum can lead to other musculoskeletal issues:

• Joint Pain: Increased stress on the knee joint can lead to pain, particularly in the lateral compartment, and may contribute to patellofemoral pain syndrome.
• Osteoarthritis Risk: Long-term altered biomechanics can accelerate wear and tear on the knee cartilage, increasing the risk of developing osteoarthritis later in life.
• Altered Gait: Individuals may develop an altered walking pattern (gait) to compensate for the misalignment, which can put strain on other joints like the hips and ankles.
• Muscle Imbalances: The condition can be both a cause and effect of muscle imbalances, with overactivity or tightness in some muscles (e.g., hip adductors) and weakness in others (e.g., hip abductors, vastus medialis obliquus).
• Foot and Ankle Issues: Compensatory pronation (flattening) of the feet may occur to help the feet make contact with the ground, potentially leading to issues like plantar fasciitis or bunions.
• Impact on Activity: For athletes, severe genu valgum can affect performance and increase injury risk in sports requiring jumping, running, or quick changes of direction.
• Cosmetic Concerns: For some, the appearance of knock knees can be a source of self-consciousness.

Causes of Genu Valgum

Genu valgum can stem from various factors:

• Physiological Genu Valgum: Most common in toddlers (ages 2-4), typically resolves spontaneously.
• Nutritional Deficiencies: Rickets (Vitamin D deficiency) is a historical cause, leading to softened bones that can bow.
• Obesity: Excess weight can place abnormal stress on growing bones and joints.
• Trauma: Fractures or injuries to the growth plates around the knee can lead to asymmetrical growth.
• Genetic Conditions: Certain genetic syndromes or skeletal dysplasias can manifest with genu valgum.
• Muscle Imbalances and Weakness: Weakness in hip abductors, gluteus medius, or core muscles, or tightness in hip adductors or hamstrings, can contribute to or exacerbate genu valgum.
• Ligamentous Laxity: Loose ligaments around the knee can lead to instability and misalignment.

Management and Treatment Strategies

Treatment for genu valgum depends on the cause, severity, and the individual's age and symptoms.

• Observation: For physiological genu valgum in children, watchful waiting is often recommended as it usually resolves.
• Physical Therapy:
  • Strengthening: Targeting hip abductors, glutes, vastus medialis obliquus (VMO), and core muscles.
  • Stretching: Addressing tight hip adductors, hamstrings, and calves.
  • Gait Retraining: Improving walking mechanics.
  • Balance and Proprioception: Enhancing neuromuscular control.
• Orthotics: Custom shoe inserts (orthotics) may be used to support the arch and correct compensatory foot pronation, which can indirectly influence knee alignment.
• Bracing: In growing children, night braces or orthoses may be used to guide bone growth.
• Weight Management: For individuals with obesity, weight loss can reduce stress on the knees.
• Surgical Intervention: Reserved for severe cases, persistent pain, or significant functional limitations, especially in adolescents or adults.
  • Guided Growth (Hemiepiphysiodesis): In children with open growth plates, a small plate or screw can be placed to slow growth on one side of the bone, allowing the other side to catch up and correct the alignment.
  • Osteotomy: In skeletally mature individuals, a wedge of bone is removed or added near the knee to realign the limb.

When to Seek Professional Advice

It is advisable to consult a healthcare professional (e.g., orthopedic surgeon, physical therapist) if:

• Genu valgum is unilateral (affecting only one leg).
• It causes pain or functional limitations.
• There is a rapid progression or worsening of the condition.
• It persists beyond the age of 8 in children.
• It is significantly impacting daily activities or quality of life.
• There are significant cosmetic concerns.

Key Takeaways

While genu valgum is a legitimate concern due to its potential impact on joint health and biomechanics, it does not typically lead to a reduction in adult height. The primary issues associated with knock knees are related to altered joint mechanics, increased risk of pain and arthritis, and functional limitations, rather than a shortening of stature. Early assessment and appropriate management, especially in growing individuals, can help mitigate potential long-term complications.