What is the cause of fifth toes overlapping or undermining the fourth toes, also known as (hammer toe) or (toe deformity)?

Medical Advisory BoardAll articles are reviewed for accuracy by our Medical Advisory Board
Educational purpose only • Exercise caution as content is pending human review
Article Review Status
Submitted
Under Review
Approved

Last updated: May 22, 2025View editorial policy

Personalize

Help us tailor your experience

Which best describes you? Your choice helps us use language that's most understandable for you.

From the Guidelines

The fifth toe undermining the fourth toe should be addressed with conservative measures, including toe spacers or separators, silicone or foam toe sleeves, and custom orthotic inserts, as well as proper footwear and pain management, with consideration for surgical correction if conservative measures fail, as recommended by the most recent guidelines on the prevention of foot ulcers in persons with diabetes (1). When managing this condition, it is essential to consider the individual's risk of foot ulceration, as classified by the International Working Group on the Diabetic Foot (IWGDF) risk stratification system (1).

  • For individuals with no or limited foot deformity, no pre-ulcerative lesions, and no plantar ulcer history (IWGDF risk 1-3), education on proper footwear and foot self-care is crucial (1).
  • For those with a foot deformity that significantly increases pressure or a pre-ulcerative lesion (IWGDF risk 2 or 3), consideration of extra-depth shoes, custom-made footwear, custom-made insoles, and/or toe orthoses is recommended (1).
  • The use of therapeutic footwear with a demonstrated plantar pressure relieving effect during walking can help prevent recurrent plantar foot ulcers in individuals with a healed plantar foot ulcer (IWGDF risk 3) (1). Key aspects of management include:
  • Proper footwear: wearing shoes that accommodate the shape of the feet and fit properly (1)
  • Foot self-care: daily foot examinations, washing feet daily, using emollients to moisturize dry skin, and cutting toenails straight across (1)
  • Pain management: using over-the-counter pain medications like ibuprofen or acetaminophen as needed (1)
  • Consideration of surgical correction: if conservative measures fail, consulting a podiatrist or orthopedic surgeon for potential surgical intervention (1)

From the Research

Fifth Toes Undermining Fourth Toes

  • The provided studies do not directly address the issue of fifth toes undermining fourth toes.
  • However, some studies discuss deformities of the fifth toe, such as overlapping and underlapping toes 2, 3, 4.
  • These deformities can cause discomfort and pain, and may require surgical intervention 2, 3, 4.
  • Another study found that clinodactyly, a deformity of the toe, is present in approximately 90% of fifth toes in newborns, and is also common in fourth toes 5.
  • A study on biphalangeal/triphalangeal fifth toes found that the presence of a triphalangeal fifth toe is associated with a higher percentage of pathological toes, including hammer toes 6.
  • While these studies provide information on deformities of the fifth toe, they do not specifically address the issue of fifth toes undermining fourth toes.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Surgical criteria for correcting the overlapping fifth toe.

The Journal of foot surgery, 1982

Research

Percutaneous correction of congenital overlapping fifth toe in paediatric patients.

Orthopaedics & traumatology, surgery & research : OTSR, 2013

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

Have a follow-up question?

Our Medical A.I. is used by practicing medical doctors at top research institutions around the world. Ask any follow up question and get world-class guideline-backed answers instantly.