There are many different ways to hurt the foot but it is diabetic neuropathy which predominantly sits as the root cause. Arterial vascular disease with narrowed arteries also contributes significantly to the gangrene and non-healing that is often seen in this condition.
Any trauma, however trivial, can induce an ulcer but there are some common scenarios that Physicians see time and time again. For example a diabetic foot can feel cold and it is normal to want to warm them up. Placing an insensitive foot in front of a fire is never a good idea and many a patient has awoken to the smell of burning flesh. Placing an insensitive foot on a hot water bottle similarly is a dangerous thing to do without pain sensation to tell you if the temperature is hot enough to induce a burn injury.
Sometimes foot pain and swelling occur spontaneously or after minimal trauma. In this situation patients and their doctors become concerned very quickly about underlying infection within the foot structure requiring immediate antibiotics. Infection within bone is a serious problem and is called osteomyelitis. This condition is often confused with an inflammatory destructive process within the main body of the foot. This is known as a Charcot foot and needs treating in a completely different way, the main focus here is to relieve all pressure on the foot until the situation has healed itself.