**Core Concept**
Wind Swept deformity is a type of angular deformity of the leg characterized by a varus deformity of the tibia and a valgus deformity of the fibula, resulting in a visible "bowing" of the leg. This deformity is often seen in conditions that affect the growth plates or the bone structure.

**Why the Correct Answer is Right**
The Wind Swept deformity is typically seen in cases of Blount's disease, a growth disorder that affects the tibia and fibula. In Blount's disease, the medial aspect of the proximal tibial epiphysis is under-ossified, leading to a varus deformity of the tibia, while the lateral aspect of the proximal tibial epiphysis is over-ossified, leading to a valgus deformity of the fibula. This results in the characteristic Wind Swept deformity.

**Why Each Wrong Option is Incorrect**
**Option A:** Rickets is a condition that affects bone mineralization, but it does not specifically cause Wind Swept deformity.
**Option B:** Osteosarcoma is a type of bone cancer that can cause deformities, but it is not typically associated with Wind Swept deformity.
**Option C:** Fibular hemimelia is a congenital defect of the fibula, but it does not typically cause the Wind Swept deformity seen in Blount's disease.

**Clinical Pearl / High-Yield Fact**
Blount's disease is a common cause of Wind Swept deformity in children, and it is often associated with obesity and overactivity during periods of rapid growth.

**Correct Answer: D. Blount's disease**