Why Do Diabetic Feet Develop Hammertoes?

When a toe contracts, it usually straightens back out. Over time, either due to arthritis, diabetes, or overuse, it can stay in a clawed or hammered position causing problems. For people without nerve damage (neuropathy), it can be painful. For people with neuropathy, it can cause ulcers.

There are a few other types of toe deformities aside from hammertoes and claw toes, and there are slightly different causes for each. However, they all can cause pain, calluses, or ulcers. Since this is a diabetic foot blog, let’s understand how diabetes contributes to toe deformities.

Diabetic Neuropathy Weakens Muscles

Foot muscles shrinking due to neuropathy

Nerves tells muscles what to do. When we have neuropathy that is severe enough, the muscles no longer receive instructions, so they start to shrink and weaken (also called muscle atrophy). Diabetic neuropathy affects the furthest part of the body first, which means the foot muscles weaken first, while the leg muscles are still normal. This creates an imbalance. Foot muscles stabilize toes at the knuckles, while leg muscles control the tips of our toes. When our leg muscles activate, the tips of our toes contract, and without our foot muscles to stabilize the toes and keep them somewhat straight, the toes end up becoming contracted over time.

Diabetes Stiffens Joints

After a long time, diabetes causes stiffening of ligaments and tendons, called glycosylation. How exactly diabetes causes this, we are not sure, but it has something to do with “AGE cross-linking” if you want to google it and read more about it. So if toes claw up every time they contract AND have stiff joints because of diabetes, they will have great difficulty straightening out. Over time, they will get pretty much stuck in a contracted position. Putting everything together, you get stiff, unforgiving, deformed toes in a foot that does not fit regular shoes well and does not feel pain. It sounds like and is indeed a recipe for disaster.

Normal toe contraction
Abnormal toe contraction due to muscle imbalance caused by neuropathy. Notice how the foot’s arch changes as well.
Clawed toes
Neuropathy causing the toes to claw and the foot to develop a higher arch, creating prominences.

There are multiple prominences created once the toes are stuck in the contracted position. These prominences are where toes ulcerate in neuropathic feet. It starts off as a callus, then evolves into a blister, then an ulcer. There are ways to treat ulcers once you get it, but the best way would be to avoid them in the first place!

So if you have hammertoes and diabetes, and are wondering what can be done, here is my quick spiel:

  • Once you have hammertoes, it can’t be reversed. It can only be surgically fixed.
  • If your hammertoes don’t hurt, I don’t recommend surgery.
  • If your hammertoes hurt and your HgA1c is below 7, then surgery may help with the pain. If your HgA1c is above 7, your risk of complications such as infection and wound healing problems may not be worth the benefit.
  • If you have diabetic neuropathy and hammertoes, watch for calluses, get your feet professionally fitted for shoes, and see a doctor as you may qualify for diabetic shoes under Medicare guidelines.

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