Based on your history and photo, this appears to be a form of localized eczema or irritant dermatitis, commonly seen behind the knees due to sweat, friction, or dryness. The redness, itching, and burning sensation are typical features.
Next Steps
You can apply Fultivate cream (fluticasone) once or twice daily for 5–7 days. Also, start using a bland, fragrance-free moisturizer twice daily—especially after bathing. Avoid hot water and harsh soaps on the area.
Health Tips
If it worsens or fails to settle, further details and clinical assessment are needed to rule out other causes like fungal infection or psoriasis. An online consultation with a dermatologist would help confirm the diagnosis and tailor treatment safely.