Knock knees, known medically as genu valgum, describe a condition where the knees angle inward, touching or nearly touching, while the ankles remain separated when standing. Genu valgum is a common orthopedic observation, particularly in young children, and often represents a normal variation in skeletal development.
Identifying Knock Knees
Identifying knock knees involves observing leg alignment when an individual stands with their feet together. In someone with genu valgum, the knees will make contact, but a noticeable space will exist between the ankles, typically three inches or more. This alignment is commonly observed in children, often becoming apparent between ages 2 and 5, with the most pronounced presentation around 3 to 4 years old. While it can affect both legs symmetrically, genu valgum can also present unilaterally, affecting one leg more than the other.
Understanding the Causes
The reasons behind genu valgum vary, ranging from normal developmental stages to underlying medical conditions. In many young children, knock knees are a physiological, temporary part of growth, often correcting naturally as they mature. This developmental type typically resolves by age 7 or 8 for most children.
A family history of genu valgum can indicate a genetic predisposition, suggesting that the condition might run in families. Nutritional deficiencies, particularly rickets, can cause knock knees. Rickets, stemming from a severe lack of vitamin D and calcium, leads to weakened bones and can result in bone malformation.
Other less common metabolic bone diseases or genetic disorders, such as skeletal dysplasias, can also contribute to genu valgum. These conditions affect bone growth and development, leading to angular deformities. Trauma or injury to the growth plates around the knee, such as a fracture, can disrupt normal bone growth and cause asymmetrical or persistent knock knees. This can happen if the injury affects the growth area of the thighbone (femur) or shinbone (tibia).
Underlying medical conditions frequently play a role, especially in cases that persist or develop later in life. Obesity, for instance, places increased stress on the knee joints, which can worsen genu valgum or contribute to its development. Inflammatory conditions, such as juvenile idiopathic arthritis, or certain genetic syndromes may also be associated with knock knees. In adults, degenerative changes like osteoarthritis can lead to or exacerbate genu valgum, particularly if there is uneven wear and tear within the knee joint.
When to Seek Medical Evaluation
While many cases of knock knees in children resolve spontaneously, certain indicators suggest the need for professional medical advice. A medical assessment is advisable if the knock knees appear severe, are rapidly worsening, or affect only one leg (asymmetry), which could point to an underlying issue.
The presence of associated symptoms such as pain in the knees, hips, or ankles, limping, or difficulty with walking or running, signals that the condition may be causing functional limitations. If knock knees develop in adolescence or adulthood, it is important to seek medical attention, as this is less likely to be a developmental variation and more likely due to an underlying cause.
Options for Management
Management approaches for genu valgum vary widely depending on the cause, severity, and the individual’s age. For physiological cases in young children, observation is the primary approach, as the condition often corrects naturally with growth. No special braces, shoes, or orthotic devices have been shown to speed up this natural resolution.
Non-surgical interventions may be considered for certain cases. Physical therapy can help strengthen muscles around the knees and improve gait. In some instances, specialized braces or orthotics might be used in children to help guide growth or support alignment, though their effectiveness in physiological genu valgum is not consistently supported. Weight management is often recommended when obesity contributes to the condition, as reducing excess weight can alleviate stress on the knees. Addressing underlying conditions, such as providing vitamin D and calcium supplements for rickets, is crucial for correcting the deformity.
Surgical options are typically reserved for severe cases that cause pain, functional limitations, or are likely to lead to future joint problems. For growing children, a minimally invasive procedure called guided growth surgery (hemiepiphysiodesis) can be performed. This involves placing a small plate or screws on one side of the growth plate to temporarily slow growth, allowing the other side to correct alignment. For older children or adults whose growth plates have closed, an osteotomy may be considered. This procedure reshapes the bone to correct alignment and is generally a more involved surgery.