Can I get cellulitis from a bee sting and how is it differntiated from the sting itself? It is next to scare from knee replacement very red

Difficult to say. You need to have it evaluated. The negative consequences from an infected total knee replacement are immense. Although it can happen, at times redness from a sting is a local reaction as opposed to cellulitis, but i would not gamble. Be seen to be sure and to get appropriate treatment.
It varies 4 everyone. Each person responds differently from not much @ all 2 a red painful & itchy lesion. Benadryl, (diphenhydramine) ice r a good place 2 start. If it's spreading & more painful or if u have knee pain & it seems infected get in 2 c u r surgeon.