As diabetic peripheral neuropathy progresses, various nerves are affected. These damaged nerves can cause problems that encourage development of ulcers. Deformities resulting from motor neuropathy result in bunion or hammertoes that may rub against other toes or the shoe can create a sore. The numbness caused by sensory neuropathy can make a patient unaware that this is happening. Additionally, cracked and dry skin caused by autonomic neuropathy, combined with sensory neuropathy numbness can also cause a sore.