One of the significant symtoms of diabetes is neuropathy in the lower legs and feet. Circulation in the legs is significant because that could be from blood clots, your medication (high blood pressure medicine, can drain your body of the necessary fluids it needs. Drinking fresh water, at least 64oz a day can help flush your body, keep it hydrated.
I will give you some sites you can find free info at, maybe one of them will help. mark's daily apple, doctor yourself from Andrew Saul (very high dose vitamin C is safe and helps relieve pain, inflammation). If these sites don't help you, I'd suggest finding a Functional Diagnostic Nutrition practitioner. They can run lab tests and will do their best to find the root causes of your problems. Also, fluoride can cause symptoms of fibromyalgia, so reduce your exposure to fluoride as much as possible and research supplementing with iodine, which will help displace fluoride from any place it has accumulated in your body.
Elevate your leg/s and apply a cold compress to your bad knee.
My physiotherapist told me to apply an ice pack to my bad knee.
As your legs are red, you should see your doctor to make sure that none of your medications are causing this. The doctor may decide whether you may need to have the bad knee xrayed to see what is going on in the knee. He may prescribe you with a different pain relief medication and/or an anti-inflammatory. Not everyone is suited to Ibuprofen and this can cause swelling with oedema also needs to be taken with food or with a medication to protect the stomach.
I do hope that you are managing to keep your sugar levels under control. It is important so that you do not get any further nerve damage.
You do not say which country you live in. In the UK people who suffer from diabetes have an annual review to ensure that their diabetes is under control and also get their eyes checked every year because of the potential of getting diabetic retinopathy.
Wishing you a speedy recovery,
Best wishes.