Question

What is the most likely cause of unilateral genu varum (bow-leg deformity of one leg) in a patient with a history of a previous injury to that limb?

(Figure: AP X-ray of both lower limbs showing bowing of one leg.)

• A. Malunion of a previous fracture
• B. Rickets
• C. Non-ossifying fibroma
• D. Osteofibrous dysplasia

Hint:

Unilateral + prior injury = malunion; rickets is bilateral and symmetric.

Answer 1

The Correct Option is A

The diagnostic anchor here is the pairing of a one-sided bow-leg with a past injury to that limb.

Angular deformities of the lower limb can be:
$\bullet$ Systemic/metabolic (e.g., rickets) - these are virtually always bilateral and symmetric, since the underlying mineralisation defect affects both legs equally.
$\bullet$ Local/structural (e.g., post-fracture malunion, physeal injury, focal bone lesions) - these can be unilateral.

Because this deformity is unilateral and tied to earlier trauma, a fracture that united in an angulated (varus) position - i.e., malunion - is the best answer. Rickets is excluded by the unilaterality; non-ossifying fibroma is typically an incidental cortical lesion; osteofibrous dysplasia is a rare paediatric tibial lesion producing anterolateral bowing, not a trauma-related varus.
\[\boxed{\text{Malunion of a previous fracture}}\]