External tibial torsion is the most common cause of out-toeingand may be associated with a calcaneovalgus foot (see Chapter201). This is often related to in utero positioning. It may improveover time, but because the tibia rotates externally with age, external tibial torsion can worsen. It may be an etiologic factor forpatellofemoral syndrome, especially when combined with femoral anteversion. Treatment is usually observation and reassurance, but patients with dysfunction and cosmetic concerns maybenefit from surgical intervention.
Available @ StudentConsult.com
The majority of patients who present with knock-knees (genu valgum) or bowlegs (genu varum) are normal (Fig. 200-2).Infants are born with maximum genu varum. The lower extremity straightens out around 18 months of age. Children typicallyprogress to maximal genu valgum around 4 years. The legs areusually straight to a slight genu valgum in adulthood.
It is important to inquire about family history and assessoverall height. A child who is 2 standard deviations belownormal with angular deformities may have skeletal dysplasia. Dietary history should be obtained, as rickets (see Chapter 31) may cause angular deformities. For genu valgum,following the intermalleolar distance (distance betweenthe two tibial medial malleoli with the knees touching) isused. Measurement of the intercondylar distance (the distance between the medial femoral condyles with the medialmalleoli touching) is used for genu varum. These measurements track improvement or progression. When obtaining radiographs, it is important to have the patella, not the feet,facing forward. In the child with external tibial torsion,having the feet facing forward gives the false appearance ofbowlegs.
Available @ StudentConsult.com
Physiologic knock-knees are most common in 3to 4-year-oldsand usually resolve between 5 and 8 years of age. Patients withasymmetrical genu valgum or severe deformity may have underlying disease causing their knock-knees (e.g., renal osteodystrophy, skeletal dysplasia). Treatment is based on reassurance ofthe family and patient. Surgical intervention may be indicatedfor severe deformities, gait dysfunction, pain, and cosmesis.
Available @ StudentConsult.com
Physiologic bowlegs are most common in children older than 18 months with symmetrical genu varum. This will generallyimprove as the child approaches 2 years of age. The most important consideration for genu varum is differentiating betweenphysiologic genu varum and Blount disease (tibia vara).
Available @ StudentConsult.com
Tibia vara is the most common pathologic disorder associated with genu varum. It is characterized by abnormal growth of the medial aspect of the proximal tibial epiphysis, resulting in a progressive varus deformity. Blount disease is classified according to age of onset:Infantile (1 to 3 years)Juvenile (4 to 10 years)Adolescent (>11 years)
Late-onset Blount disease is less common than infantile disease. The cause is unknown, but it is felt to be secondary to growth suppression from increased compressive forces across the medial knee.
Infantile tibia vara is more common in African Americans, females, and obese patients. Many patients were early walkers.
Nearly 80% of patients with infantile Blount disease have bilateral involvement. It is usually painless. The patients will often have significant internal tibial torsion and lower extremity leg-length discrepancy. There may also be a palpable medial tibial metaphyseal beak.
Late-onset Blount disease is more common in African Americans, males, and markedly obese patients. Only 50% have bilateral involvement. The initial presentation is usually painful bowlegs. Late-onset Blount disease is usually not associated with palpable metaphyseal beaking, significant internal tibial torsion, or significant leg-length discrepancy.