Lower limb alignment naturally shifts through different angles as a child grows. This progression is part of human development, reflecting the skeletal structure adapting to walking and weight-bearing stresses. While most children’s legs will self-correct to a neutral position, some deviations may persist, leading to medically recognized conditions that describe the specific angular difference at the knee joint. Understanding these conditions requires looking at the two primary extremes of this alignment spectrum.
Understanding Bow-Leggedness (Genu Varum)
Bow-leggedness is medically termed Genu Varum, where the lower limbs curve outward. When standing with feet and ankles together, a noticeable, outward-curving gap exists between the knees. This appearance is often a normal, temporary stage in infants, called physiologic genu varum, resulting from the fetal position. Physiologic bowing typically begins to resolve and straighten by about 18 months of age, with most children achieving neutral alignment around two years old. If the outward curve remains pronounced past age two, or if it affects only one leg, it may indicate a pathological cause requiring medical evaluation.
The Opposite Alignment: Knock-Knees (Genu Valgum)
The exact opposite alignment of bow-leggedness is known as knock-knees, or Genu Valgum, where the lower legs angle inward at the knee joint. This structural characteristic causes the knees to touch or overlap when the person stands with their ankles separated. To assess the severity of Genu Valgum, a healthcare provider will often measure the distance between the inner ankles (intermalleolar distance) while the knees are held together. Like Genu Varum, this inward angulation is a natural, developmental phase that follows the outward bowing of infancy. Children usually begin to develop this knock-kneed appearance around age two, with the angle peaking between three and five years old. The legs then typically correct themselves toward the normal, slightly angled adult alignment by the time the child reaches approximately age seven or eight.
Common Causes and Developmental Timelines
The progression from Genu Varum (bow-leggedness) to Genu Valgum (knock-knees) and then to a neutral stance is the standard developmental timeline for lower limb alignment. This predictable pattern occurs as the hip and knee joints mature and adapt to a bipedal gait.
When alignment falls outside this expected range or persists longer than normal, it may signal a pathological condition. One common cause is Rickets, a bone growth disorder resulting from a severe deficiency in Vitamin D, calcium, or phosphorus. Rickets causes the bones to soften, potentially leading to either Genu Varum or Genu Valgum. Another specific cause of pathological bowing is Blount’s disease, a growth disturbance affecting the growth plate on the inner side of the shin bone (tibia). Skeletal dysplasias, which are genetic disorders affecting bone development, are other potential underlying causes for extreme angulations.
When and How Alignment Issues Are Treated
For the majority of cases, which are physiological, the primary medical approach is simply observation and monitoring to confirm the natural correction of the alignment over time. Healthcare providers track the child’s growth and measure the inter-knee or inter-ankle distance during regular physical examinations. If a nutritional deficiency like Rickets is identified, treatment focuses on medical management, often involving dietary adjustments to include Vitamin D and calcium, sometimes with the help of a specialist.
Intervention is generally reserved for cases that are severe, painful, asymmetrical, or those that persist significantly beyond the expected age of correction, suggesting a pathological cause. For younger children with Blount’s disease, bracing may be used to help guide the bone’s growth. Surgical procedures are considered for older children or adolescents with severe, progressive deformities. These procedures include guided growth, where a small plate or staple is temporarily placed on one side of the growth plate to slow growth on that side, allowing the other side to catch up and straighten the limb. Alternatively, an osteotomy may be performed, which involves surgically cutting and reshaping the bone to immediately correct the angle.