Genu Valgum, commonly known as knock knees, is a lower limb alignment where the knees angle inward and touch while the ankles remain separated. This condition is frequently observed in children, often prompting concern about potential long-term effects on physical development. The question of whether this misalignment can restrict overall linear growth requires a clear, science-based examination.
Understanding Genu Valgum
The presentation of inward-angling knees is a normal and expected part of developmental physiology in early childhood. This developmental form, known as physiological Genu Valgum, typically begins to appear around age two and reaches its peak severity between ages three and four.
The vast majority of children experience spontaneous correction as they grow, with legs gradually straightening to a normal adult alignment by age seven or eight. Pathological Genu Valgum occurs when the misalignment is severe, asymmetrical, or persists beyond the typical age of resolution. These concerning cases are often linked to underlying medical conditions, such as metabolic bone diseases like rickets or skeletal dysplasias.
The Direct Relationship Between Knock Knees and Height
The primary concern regarding Genu Valgum and height centers on its potential interference with the growth plates, or physes, located at the ends of the long bones. Linear growth is determined by the activity of these plates, primarily in the femur and tibia. In cases of typical, physiological knock knees, the alignment does not interfere with the normal function of these growth centers.
Standard Genu Valgum does not affect a child’s ultimate height potential. The condition is merely a temporary phase of skeletal development, and the growth plates continue their vertical lengthening activity unimpeded.
Severe, pathological Genu Valgum, however, can be a symptom of systemic disorders that impact height. Conditions like rickets or certain skeletal dysplasias disrupt the normal process of bone formation and growth, leading to both short stature and severe leg deformities. In these instances, the underlying systemic disease is the cause of both the height restriction and the misalignment, not the knock knees themselves. The deformity can create abnormal mechanical stress on the physes, but the root cause is the disease affecting the bone structure.
Functional Impacts Beyond Height
While the effect on linear growth is minimal for most people, Genu Valgum introduces significant biomechanical changes that impact movement and joint health. The altered alignment shifts the mechanical load-bearing axis of the leg outward, placing increased stress on the lateral compartment of the knee joint. This weight distribution abnormality can lead to an altered walking pattern, sometimes described as a circumduction gait, where the individual swings their leg outward to avoid the knees knocking together.
Increased strain on the knee joint also contributes to patellar instability, as the kneecap is pulled laterally from its normal groove. Over a long period, this chronic mal-alignment increases the risk of developing pain in the knees, hips, or ankles due to abnormal forces. For adults whose Genu Valgum did not self-correct, this uneven load can lead to the premature development of osteoarthritis in the knee.
When Intervention is Necessary
Medical intervention is rarely required for the common physiological form of knock knees, which corrects naturally. A consultation with a specialist is recommended if the misalignment is asymmetrical, causes pain, or persists beyond seven or eight years of age. Pathological misalignment is often defined by a severe angle, such as a tibiofemoral angle greater than 15 degrees or an intermalleolar distance greater than 8 centimeters.
For mild, persistent cases, non-surgical management may involve targeted physical therapy or the use of orthotics, though these are not effective at correcting the underlying bone alignment. For children who are still growing, the preferred surgical method is guided growth surgery, or hemiepiphysiodesis. This minimally invasive procedure involves temporarily placing a small plate or screw on the inner side of the growth plate to slow growth on that side, allowing the outer side to catch up and gradually straighten the limb.
This guided growth technique is effective because it harnesses the child’s remaining growth potential to correct the angle. Once skeletal maturity is reached, or in cases of extreme severity, the only remaining option is an osteotomy. This invasive procedure involves surgically cutting and reshaping the bone, typically the femur, to immediately restore proper alignment.