Shin curvature, often referred to as bowed legs or genu varum, describes a condition where the legs curve outward at the knees, creating a noticeable gap when the ankles are brought together. While some leg shape variation is a normal part of human development, particularly in early childhood, other instances of shin curvature can indicate underlying medical considerations.
Understanding Normal Bone Development and Variation
Some outward curvature in the legs is a common and normal aspect of development, especially in infants and toddlers. This phenomenon, known as physiological bowing, is often present at birth due to the baby’s position in the womb. As a child begins to stand and walk, usually between 12 and 18 months, this bowing may become more apparent but generally corrects itself. Most children outgrow physiological bowing without intervention by around 2 to 3 years of age, with complete resolution often seen by age 4.
The leg shape then shifts to a “knock-knees” (genu valgum) appearance around ages 3 to 4, before gradually straightening to a more neutral alignment by about age 6 or 7. Adult leg shape can also vary naturally, with some individuals retaining a slight degree of bowing that falls within normal variation.
Underlying Medical Conditions Leading to Shin Curvature
While physiological bowing is common, persistent or severe shin curvature can signal an underlying medical condition. Rickets and Blount’s disease are two primary conditions that can lead to abnormal shin curvature. These conditions disrupt normal bone growth and mineralization, resulting in deformities that extend beyond typical developmental patterns.
Rickets is a bone disease primarily affecting children, characterized by soft and weakened bones due to deficient mineralization at the growth plates. It is most often caused by a lack of vitamin D, calcium, or phosphorus, essential for healthy bone development. Beyond bowed legs, signs of rickets can include bone pain, muscle weakness, delayed growth, and sometimes dental problems or an enlarged forehead. Untreated, rickets can lead to permanent deformities and reduced height.
Blount’s disease, also known as tibia vara, is a growth disorder affecting the growth plates of the shin bone (tibia) near the knee. This condition causes the lower leg to curve inward, often resembling a “C” shape. It manifests in two forms: infantile, typically appearing in children between 1 and 3 years old, and adolescent, usually presenting after age 10. The infantile form is more prevalent and often affects both legs, while the adolescent form is less common and may affect only one leg. Risk factors include early walking, being overweight, and a family history. Unlike physiological bowing, the curvature in Blount’s disease worsens over time if untreated, potentially leading to discomfort, difficulty walking, and knee arthritis.
Other less common conditions can contribute to shin curvature. Paget’s disease of bone, a chronic disorder of bone remodeling, can cause bones to become enlarged and misshapen, leading to bowed legs, particularly in older adults. Rare bone dysplasias or genetic conditions affecting bone development can also result in shin curvature. Additionally, improperly healed fractures can sometimes lead to bone deformities, including bowing.
When to Seek Professional Medical Guidance
While physiological bowing typically resolves on its own, certain indicators suggest the need for medical evaluation. If the curvature appears to be worsening over time, particularly after a child reaches 2 or 3 years of age, medical consultation is advisable.
Concerns also arise if the bowing affects only one leg or if there is noticeable asymmetry between the legs. Accompanying symptoms like pain in the hips, knees, or ankles, limping, or difficulty walking are also red flags. Any sudden onset of shin curvature, especially in an older child or adult, or if a child is unusually short for their age, warrants prompt medical assessment.
Diagnostic Approaches and Management Options
Medical professionals employ several methods to determine the underlying cause of shin curvature. A thorough physical examination is typically the first step, where the doctor assesses the leg alignment, measures the distance between the knees, and observes the walking pattern. Medical history, including family history and dietary habits, also provides valuable insights.
Imaging tests, such as X-rays, are frequently used to visualize the bone structure and growth plates, helping to differentiate between normal development and conditions like Blount’s disease or rickets. Blood tests may be ordered to check for nutritional deficiencies, such as low vitamin D or calcium levels, which are characteristic of rickets.
Management options depend on the specific diagnosis and severity. For nutritional rickets, treatment involves dietary changes, including increased vitamin D and calcium intake, and often oral vitamin D supplements. Improvements can sometimes be seen quickly, with deformities potentially resolving if treated early in childhood.
For Blount’s disease, particularly in young children with mild to moderate cases, non-surgical approaches like bracing or orthotics may be effective. These custom-made braces aim to guide the legs into a straighter position as the child grows. If bracing is unsuccessful or for more severe or progressive cases, surgical intervention may be necessary. Surgical procedures include osteotomy (cutting and realigning the bone) or guided growth techniques (placing a small plate or staple near the growth plate to correct the deformity over time). Physical therapy can also improve mobility and strengthen leg muscles.