Tibial varus is a common orthopedic condition that involves an inward bowing of the lower leg, specifically affecting the tibia, or shin bone. This angular deformity can impact an individual’s gait and overall limb alignment. The condition can range from a mild deviation that resolves naturally to a more pronounced bowing that may require intervention.
Understanding Tibial Varus
Tibial varus describes an alignment where the lower leg bows outward, causing the knees to appear separated while the ankles remain close together. Visually, this results in a “bowed leg” appearance. The anatomical basis of tibial varus involves the tibia, the larger of the two bones in the lower leg, and its alignment relative to the femur, the thigh bone.
It is important to distinguish between physiological varus and pathological varus. Physiological genu varum, or bowed legs, is a normal developmental stage observed in infants and toddlers, typically resolving spontaneously by around 2 years of age. The tibiofemoral angle, which measures the alignment between the thigh and shin bones, usually reaches a neutral position between 18 to 24 months, then shifts to a slightly knock-kneed (valgus) alignment around 3 years, before settling into a normal adult alignment by age 6 or 7. Pathological varus, however, is a persistent or worsening condition beyond this typical developmental curve, necessitating medical attention.
Causes and Risk Factors
Tibial varus can stem from a variety of underlying causes, often involving disruptions in bone growth and development. One notable cause is Blount’s disease, also known as tibia vara, which is a developmental disorder characterized by abnormal growth of the medial (inner) aspect of the proximal tibial physis, or growth plate. This condition results in a progressive lower-limb deformity that includes varus angulation.
Other conditions contributing to tibial varus include rickets, a bone disorder caused by prolonged vitamin D deficiency, which weakens growth plates through delayed ossification. Trauma, such as injuries to the growth plate, or infections like osteomyelitis, can also lead to asymmetric growth disturbances and subsequent bowing. Certain genetic predispositions and other metabolic bone disorders may also play a role in the development of pathological varus.
Risk factors associated with conditions like Blount’s disease include early walking, particularly before 12 months, and obesity, as increased mechanical stress on the growth plates can inhibit normal bone formation. There is also a higher prevalence of Blount’s disease in individuals of Hispanic and African American descent.
Identifying Tibial Varus
Recognizing tibial varus often begins with observing visible bowing of the legs, particularly when a child stands with their feet together and their knees remain separated. Individuals may also experience knee pain, commonly on the inside aspect of the knee, due to altered weight distribution. Gait abnormalities, such as a waddling walk or an inward rotation of the feet, can also be present. These symptoms may lead to difficulty with physical activities, including running or prolonged standing.
Healthcare professionals diagnose tibial varus through a comprehensive physical examination, which includes assessing leg alignment and observing gait patterns. Measurements of leg alignment, such as the tibiofemoral angle, help quantify the degree of bowing. Imaging studies, primarily full-length standing X-rays of the lower limbs, are used to determine the severity and precise angles of the deformity. These X-rays allow for the measurement of specific angles, such as the metaphyseal-diaphyseal angle (MDA) in the tibia, with an MDA greater than 11 degrees often indicating Blount’s disease.
Management and Treatment Approaches
Managing tibial varus varies depending on the patient’s age, the severity of the bowing, and its underlying cause. For physiological varus in young children, observation is a common approach, as the condition often corrects itself as the child grows.
When the bowing is more pronounced or progressive, non-surgical options may be considered. Bracing, using orthotics like knee-ankle-foot orthoses (KAFOs), can be used in younger children to help guide bone growth. Physical therapy may also be prescribed, focusing on strengthening exercises for leg muscles and gait training to improve walking patterns and reduce stress on the knee joint.
For more severe or progressive cases, surgical interventions may be necessary to correct alignment, reduce pain, and prevent long-term complications such as osteoarthritis. One common surgical procedure is an osteotomy, where the bone, usually the tibia, is cut and reshaped to correct the angular deformity. This can involve either acute correction, where the bone is immediately realigned, or gradual correction using external fixation devices.
Another technique is guided growth, or hemiepiphysiodesis, which is a less invasive procedure primarily used in growing children. This involves temporarily slowing the growth on one side of a bone’s growth plate, often using small plates or screws, to allow the other side to catch up and correct the alignment over time.