The continued use and pressure destroys the body's attempts at healing. In due course the idea that it will not heal is accepted by everyone. It is not that it WILL NOT heal, but it is not given a chance to heal. Every attempt to heal is frustrated by further trauma falling on the healing tissues. Never underestimate the severity of an ulcer on a weight bearing or pressure area.
Most primary ulcers are the result of direct trauma.
The first ulcer may follow an obvious accident a step on a stone or a puncture by a nail, but because of NO PAIN the lesion is neglected and the ulcer becomes chronic. A person with normal sensation would alter their gait to prevent pain when walking on the ulcer, but the patient with sensory neuropathy will continue to walk as if nothing was wrong. The more chronic the ulcer, or the slower it heals, the more scar tissue will be left when it does heal. Scar tissue is more prone to ulceration than normal skin. Scarred skin is ulcer liable.