The appearance of curved shins often prompts questions about lower leg alignment. This visible curvature can occur at any age, from infancy through adulthood. While many instances are a normal part of human development and require no intervention, certain patterns can signal an underlying medical condition. The distinction between a normal developmental stage and a progressive disorder is based on the curve’s symmetry, severity, and whether it resolves naturally over time.
Defining Different Types of Leg Curvature
Leg curvature is generally categorized by the direction the knees point relative to the ankles. The most common type is bowing, medically termed genu varum, where the knees angle outward, creating a noticeable space between them when the ankles touch. This results in the characteristic bow-legged appearance. Conversely, genu valgum, or knock knees, describes an inward angulation where the knees touch or overlap while the ankles remain apart. These are coronal plane deformities involving alignment from the hip to the ankle. A less common type is anterior curvature, a front-to-back bowing of the tibia, or shinbone. This can make the lower leg look slightly “S”-shaped when viewed from the side.
Developmental and Disease-Related Causes
The majority of leg bowing observed in children is physiologic bowing, a normal part of skeletal maturation. Infants often have some bowing due to their cramped position in the womb. This alignment is typically symmetrical and slowly corrects itself as the child begins bearing weight and walking, usually resolving completely between the ages of three and five years. Pathological bowing fails to correct or progressively worsens, indicating an underlying condition.
One cause is Blount’s disease, or tibia vara, which results from a growth disturbance on the inner side of the proximal tibial growth plate. This condition leads to a sharp, abrupt angulation just below the knee, often affecting only one leg or presenting asymmetrically. Another pathological cause is Rickets, stemming from a deficiency in Vitamin D, calcium, or phosphate that prevents proper bone mineralization. Rickets causes bones to soften and bend under the body’s weight, resulting in a gradual and symmetrical bowing of both legs. Post-traumatic deformities, such as those from a poorly healed shinbone fracture, can also create a persistent or unilateral curve.
Assessing Pain and Functional Limitations
While cosmetic concerns may prompt an inquiry, pain or functional limitation strongly indicates that the curvature is pathological or progressive. Bowing that creates uneven weight distribution places excessive pressure on the inner side of the knee joint. Over time, this chronic imbalance can lead to pain in the knees, hips, and ankles. Significant angular deformities can also cause noticeable gait abnormalities, such as a waddling walk or a lateral thrust of the knee when walking. The lateral thrust is the knee joint momentarily shifting sideways with each step, which can destabilize the joint. A rapidly progressing or noticeably asymmetrical curve suggests the alignment is not a benign developmental variation.
Medical Evaluation and Corrective Measures
A medical evaluation is recommended if a child’s leg bowing persists past age three, is asymmetrical, or is accompanied by pain. The diagnostic process begins with a physical examination, where the physician observes the individual’s posture and gait. Standing X-rays of the entire leg, from hip to ankle, are necessary to measure the degree of angulation and determine the deformity’s precise location. If Rickets is suspected, blood tests check Vitamin D and calcium levels to confirm a nutritional deficiency. Treatment depends on the cause and the patient’s age. Physiologic bowing requires only observation and periodic follow-up to ensure natural correction. For growing children with progressive deformity, non-surgical options like bracing may be used to guide growth. More severe or persistent cases, especially in adolescents and adults, often require surgical intervention.
Surgical Procedures
- Guided Growth: This procedure uses small plates or staples to slow growth on the healthy side of the bone, allowing the curved side to straighten.
- Osteotomy: For skeletally mature individuals, an osteotomy involves cutting and realigning the bone to correct the mechanical axis and prevent future joint degeneration.