Differential Diagnosis of Unilateral Tibial Bowing

Anterolateral bowing

• Neurofibromatosis type 1 (shown above): Can be unilateral. Fibula may or may not be hypoplastic.
• Congenital anterolateral tibial bowing and polydactyly (CATBP)

Anteromedial bowing

• Fibular hemimelia: Linked to the sonic hedge-hog gene. May also see skin dimpling over the tibia, equinovalgus foot, missing lateral toes, and tarsal coalition.

Posteromedial bowing

• Calcaneovalgus foot deformity: resolves with growth. Also associated with limb-length inequality and triceps surae weakness.

Lateral bowing

• Physiologic in infants
• Abnormalities of the medial physis: Fracture malunion, Blount disease, Turner syndrome, rickets, hypophosphatasia
• Fibrocartilaginous dysplasia At the site of pes anserinus tendon insertion.

Special thanks to Dr. James Dimaala for the case of anterolateral tibial bowing in a patient with neurofibromatosis type I.