Thank you for asking, vasculitis
with surgical intervetions of the knee can complicate the the vasulature which passess through the popliteal fossa
. if there is no diabetes
and all other negative nitrogen balances are rule out. then i am sure your vasculature needs to be assessed for. One other chance of non healing ulcer can be malignancy, So you need a dermatologist
to rule out laater and an endovascular surgeon to rule out former.
Go get them