Windswept Deformity (CP / Rickets)

This asymmetric pattern - genu valgum, or knock-knee, in one leg and genu varum, or bow-leg, in the other, so the legs appear swept to one side - is a windswept deformity. The most important conceptual point is that it is a sign, or symptom, with many possible causes rather than a single disease, so my job is to find the underlying cause before treating. The aetiologies fall into groups, and the largest is rickets and other metabolic bone disease - nutritional or hypophosphataemic rickets and renal osteodystrophy - followed by skeletal dysplasias and other genetic disorders, trauma with physeal injury or malunion causing asymmetric growth, and an idiopathic or descriptive group, classically otherwise-healthy young children of African descent presenting at two to three years; neuromuscular disease such as cerebral palsy is a classic cause of the windswept pattern, especially at the hips, with one hip abducted and the other adducted. So my work-up is a careful history and examination, full-length standing alignment radiographs to characterise and localise the deformity, and crucially a metabolic screen - calcium, phosphate, alkaline phosphatase, vitamin D and renal function with PTH - to detect rickets or metabolic disease, with genetic assessment if a dysplasia is suspected. Management is aetiology-directed: I would treat rickets or metabolic disease medically, since correcting it may resolve or stabilise much of the deformity, and manage any dysplastic or cerebral-palsy context; then I would correct residual or structural deformity orthopaedically, with guided growth, hemiepiphysiodesis, in the growing child or osteotomy for established deformity. The error to avoid is operating while missing a treatable metabolic cause.