Brief Answer:
Due to injury or raised blood pressure

Detailed Answer:
Hello,

Thanks for writing to us,
I have studied your case with diligence.

There are some important causes for ankle swelling,

Injury to ankle leads to swelling, if you are having any history of trauma then that can be reasons for swelling. X XXXXXXX of ankle will help in diagnosis.

As you are having diabetes, and at age of 81 there can be associated hypertension leading to swelling over ankle and foot. You need to check your blood pressure and if raised start medication accordingly.

Cellulitis is common in diabetic patients which leads to ankle and leg swelling, you may need clinical examination to rule out .Rest and antibiotic can control infection.
Renal insufficiency can lead to ankle swelling; blood investigation like renal function test will help in diagnosis.
I will advise to consult your treating doctor so that after clinical examination he can advise required investigation and treatment accordingly.

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.

Take care

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