What Causes Swelling And Redness In The Left Ankle?

went to ER yesterday, left ankle is swollen red on both sides and the top of my foot close to the bend. also my sed rate was elevate and my white count was high this did not happen thru a trauma, the ER DR was concerned that I had septic arthritis they sent me to another hospital, where the day shift DR was also concern about the same, she aspirate twice barely any fluid maybe 2 small drops, very small, they changed shifts, then told me it was cellulitis, gave me a iv bag of 1000 milligrams Vancomycin sent me home with cephalexin 500 mg for 10 days. my ankle is redder and warmer today, I have a follow with my PCP Monday morning. I m just having hard time believing that its cellulitis. I understand you can t see it, but from I have described does it sound like cellulitis.