Thanks for writing to us.
You probably have ecchymotic patch with mole and crusted lesion on the knee.
This much description is less to come to conclusion.
Therefore, I would like to ask few questions.
Do you have itching, burning or pain in lesion?
Do you have Fever
or joint pain?
Duration of the disease?
Past history of same or other disease?
Family history of disease?
Any habit of alcohol or smoking?
Did contact any doctor?
Did you take or apply any medicine?
Any blood test?
Please answer above questions.
I would like to have close up photograph of the lesion. You have a feature to upload the images by yourself on the right side of this query page. Please utilize it.
I do hope that you have found something helpful and I will be glad to answer any further query.