If your work involves bending the knees or kneeling, then warfarin
can cause easy bruising
. Yes, rash due to the drug is possible, but is usually bilateral, and generalized. For localized itch rash on
your knees you must think in lines of allergic dermatitis, eczema, scabies, con
tact dermatitis, shingles, psoriasis, fungal infection
like or Tinea.
It is difficult to comment beyon
d this at this stage without examining the rash. Please con
sult a skin specialist. Take care!