Callus

Why do we develop calluses? The formation of callus is a protective mechanism used by the skin to respond to external mechanical irritation.  Any area of skin can form callus, but the most common locations for callus on the foot include the bottom of the foot, the side of the foot or even between the toes. Regardless of location, the cause of the callus is going to be external pressure that pushes against a boney prominence. The skin becomes irritated and thickens in response to this mechanical irritation.  This thickening of the skin is what we call callus.  What is the cause of this external pressure? External pressure can be due to the ground (affecting the bottom of the foot), the shoe (affecting the sides or the top of the foot) or even and adjacent toe (affecting between the toes).

By definition, the build up of protective skin on the bottom of the foot is called a callus. If the same problem occurs on the toes, it's called a corn. There's a host of different types of calluses some of which are described in the nomenclature section of this page (see below).

The most common spot for callus is on the ball of the foot just behind each of the five toes. The ball of the foot is actually anatomically analogous to the area of the palm of the hand where we tend to form callus. Both of these areas are load bearing surfaces and areas of bony protrusion.

Another common area of callus on the foot is on the rim of the heel.  Heel callus, or what are often called heel fissures are a unique form of callus that form from tension placed upon the rim of the heel. 

The presence of a callus does not necessarily indicate that there's a foot problem.  Most calluses do not require the care of a doctor and can be treated at home with topical medicated callus creams and periodic debridement.

Heel fissure - thick cracked heels. Often found in folks who are over weight.

HD - see heloma dura.

Hellom dura - hard corn. Typically used to describe corns of the top of the toes.

HM - see heloma molle.

Helloma molle - soft corn found between the toes.

Intractable plantar keratoma - a callus that has a distinct plantar core in the center of the callus

IPK - see intractable plantar keratoma.

Kissing corn - see heloma molle.

Lister corn - small corn found on the inner or outer margins of the 5th toe nail.

Pinch callus - a callus of the plantar medial great toe joint or great toe.

Spin Callus - see pinch callus.

Shear Callus - callus formed by friction. Shear calluses are typically longitudinal and deep with multiple recesses.

Tyloma - a thick broad callus found on the bottom of the forefoot.

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Many calluses are the result of a unique pattern of wear specific to the way we walk. A spin callus, also called a pinch callus, is an example of a unique gait pattern due to a limited range of motion at the 1st metatarsal phalangeal joint (big toe joint). As we push off with each step, a limited range of motion at the 1st mpj forces us to spin on the plantar medial surface of the great toe. When watched from behind, a person with a pinch callus will have a twist or pivot as they 'toe off'.

Most calluses have to a degree some biomechanical origin. Your podiatrist or pedorthists should be able to explain many different biomechanical factors that can contribute to the formation of callus.

Not all calluses are painful. But as a callus thickens, we tend to see increased pain due to pressure applied to the soft tissue beneath the callus. Thinning the callus by debridement with a safety shaver, callus file and callus cream will often control painful calluses. Callus pads can be used to decrease load applied to the callus.

In severe cases, callus can lead to an ulceration of the soft tissue beneath the callus. This is particularly common in patient who have lost sensation in their feet due to diabetes.  If you have diabetes, neuropathy or poor circulation, be sure to consult your podiatrist for periodic callus care.

Callus is a condition that can vary in both location and appearance. The differential diagnosis for this condition should include;

Abscess
Blister
Benign soft tissue tumor including a glomus tumor, porokeratosis or eccrine poroma.
Malignant soft tissue tumor including malignant melanoma and Kaposi's sarcoma.
Psoriasis
Ulcer
Verrucae/Wart

• Heel and Skin Fissures

• Skin

• Fungus Toe Nail

• Toe Box Dermatitis

• Dry Skin

This article was written by Jeffrey A. Oster, DPM and last updated 2/5/13.

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