Hi Sally,
Sorry to hear of your father's problems and that he has to have a major leg operation in 4 weeks. It'll be relevant as to whether the diabetes diagnosis of Type 2 or Type 1. Maybe Type 2 because that's the one that people tend to develop in later life - they used to call it 'age-onset' diabetes.
I'm 66 years old myself and I was diagnosed as a Type 2 myself just over nine years ago - and I'm fust fine. They are always concerned about operating on any person with diabetes because it does cause complications. I needed an operation for bowel cancer not long after my diagnosis and the hospital people were quite concerned but really, in my case, they didn't have any choice but to operate. The outcome was excellent and I recovered quickly - out of hospital in 8 days instead of the predicted 10 days minimum. Also, back at work in less than a month.
Diabetes is a very serious disease and can become quite nasty. However, any level of problem either for the operation or for life in general all comes down to how well people control their condition. Great control of diabetes can be effected through diet - mainly, cutting out sugary food but also in cutting back on starchy carbohydrate foods - i.e. cereals, bread, potatoes, pasta and rice. My diabetes worsened for eight years by following the NHS advice that I was given. However, I've normalised my blood glucose levels over the last eighteen months mainly by changing my diet.
You are right to be concerned but do not become over anxious because there is no reason why your father should have any major problems if he adjusts his diet to take control of his condition.
It's good to hear that he is having a knee replacement operation and not one related to his diabetic condition?
Maybe you can learn something about how to control Type 2 diabetes from my experiences that are documented in postings elsewhere on this forum:
This first one is about my current diet and might be useful to improve your father's blood glucose levels in the four weeks leading up to his operation:
http://www.diabetessupport.co.uk/boards/showthread.php?t=6435&highlight=reversal
This other posting is about how things happened to me over nine years and tells a story of how bad the advice is that is usually given to people with Type 2.
http://www.diabetessupport.co.uk/boards/showthread.php?t=3961&highlight=reversal
I hope that everything will go well with his operation and that you will be able to get your father to take control of his condition.
Very best wishes to both of you - John