I have studied your case.
As per your history and symptoms possibility of cellulitis with dermatitis
can be considered.
To diagnose septic arthritis
look for local raised temperature,severe pain
,pain on joint movement,fever.
You may need to investigate in form of complete blood count
, ESR, CRP,
Septic /cellulitis can be confirmed, and antibiotic can be started according to examination.
Joint aspirate may help in diagnosis.
Hope this answers your query. If you have additional questions or follow up queries then please do not hesitate in writing to us. I will be happy to answer your queries.
Wishing you good health.