Trapezoid Bone

Last updated: February 8, 2026Reviewed date: February 8, 2026Reading time: 5 min read
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Article Summary

A trapezoid, also known as a trapezium is the first and most lateral of the distal row of carpal bones is a flat closed shape having 4 straight surfaces or sides, with one pair of parallel sides found within the hand. The parallel sides of a trapezium are known as the bases, the broad end of the wedge constituting the dorsal, the narrow end the palmar surface;...

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Definition

A trapezoid, also known as a trapezium is the first and most lateral of the distal row of carpal bones is a flat closed shape having 4 straight surfaces or sides, with one pair of parallel sides found within the hand.

The parallel sides of a trapezium are known as the bases, the broad end of the wedge constituting the dorsal, the narrow end the palmar surface; and their non-parallel sides are called legs. A trapezium can also have parallel legs, and parallel sides can be horizontal, vertical, or slanting.

Surfaces

The superior surface, quadrilateral, smooth, and slightly concave, articulates with the scaphoid. The inferior surface articulates with the proximal end of the second bone; it is convex from side to side, concave from before backward, and subdivided by an elevated ridge into two unequal facets.

The lateral surface, convex and smooth, articulates with the trapezium. The medial surface is concave and smooth in front, for articulation with the capitate; rough behind, for the attachment of an interosseous .

The dorsal and palmar surfaces are rough for the attachment of , the former being the larger of the two.

The trapezium bone is bordered medially by the trapezoid bone and superiorly by the scaphoid bone. Inferolaterally, its main articulation is with the first metacarpal bone via a saddle-shaped facet. Inferomedially however, it sometimes also articulates with the second metacarpal bone.

Distally, it forms a stable, relatively immobile joint with the second metacarpal, radially and proximally it forms strong ligaments with the trapezium and the capitate clearly, scaphoid respectively.

However, injury can occur through axial force applied to the second metacarpal base. Subluxations, such as ones caused by delivering a blow, are not uncommon. Direct to the bone can also cause a .

On the palmar aspect of the bone, there is a palpable tubercle and on its medial side runs a groove that holds the of the flexor carpi radialis. it is bound by strong ligaments to the trapezium radially, the capitate clearly, and the scaphoid proximally. Its shape is like a keystone, and it is two times wider dorsally than primarily.
The trapezoid may look very small as compared to the opposite bones from a palmar aspect, however, it’s much wider on its dorsal side. It communicates via its proximal facet with the os scaphoideum, laterally with Trapezium bone, medially with the capitate and its distal facet allows it to articulate with the second metacarpal.The carpal bones are aligned in proximal and distal rows. The proximal carpal row from the radial side consists of the scaphoid, lunate, triquetrum, and pisiform bones. The distal carpal row from the radial side is formed from Trapezium, trapezoid, capitate, and hamate bones. The carpal bones are held together by the interosseous, volar, and dorsal ligaments and a triangular fibrocartilage complex. The dorsal ligaments are weaker than the volar ligaments, making dorsal more common.

References

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Doctor visit helper

Prepare before seeing a doctor

A simple rural-patient checklist to help you explain symptoms clearly, ask better questions, and avoid unsafe self-treatment.

Safety note: This is not a prescription or diagnosis. For severe symptoms, pregnancy danger signs, children with serious illness, chest pain, breathing difficulty, stroke-like weakness, or major injury, seek urgent care.

Which doctor may help?

Start with a registered doctor or the nearest qualified health center.

What to tell the doctor

  • Write when the problem started and how it changed.
  • Bring old prescriptions, investigation reports, and current medicines.
  • Write allergies, pregnancy status, diabetes, kidney/liver disease, and major past illnesses.
  • Bring one family member if the patient is weak, elderly, confused, or a child.

Questions to ask

  • What is the most likely cause of my symptoms?
  • Which danger signs mean I should go to hospital quickly?
  • Which tests are necessary now, and which can wait?
  • How should I take medicines safely and what side effects should I watch for?
  • When should I come for follow-up?

Tests to discuss

  • Vital signs: temperature, pulse, blood pressure, oxygen saturation
  • Basic physical examination by a clinician
  • CBC, urine test, blood sugar, or imaging only when clinically needed

Avoid these mistakes

  • Do not use antibiotics, steroid tablets/injections, or strong painkillers without proper medical advice.
  • Do not hide pregnancy, kidney disease, ulcer, allergy, or blood thinner use.
  • Do not delay emergency care when danger signs are present.

Medicine safety and first-aid guide

This section is for patient education only. It does not replace a doctor, pharmacist, or emergency care.

Safe first steps

  • Rest, drink safe water, and observe symptoms carefully.
  • Keep a written note of symptoms, duration, temperature, medicines already taken, and allergy history.
  • Seek medical care quickly if symptoms are severe, worsening, or unusual for the patient.

OTC medicine safety

  • For mild pain or fever, ask a registered pharmacist or doctor before using common over-the-counter pain/fever medicines.
  • Do not combine multiple pain medicines without advice, especially if you have kidney disease, liver disease, stomach ulcer, asthma, pregnancy, or take blood thinners.
  • Do not give adult medicines to children unless a qualified clinician advises it.

Avoid these mistakes

  • Do not start antibiotics without a proper medical decision.
  • Do not use steroid tablets or injections casually for quick relief.
  • Do not delay emergency care because of home remedies.

Get urgent help if

  • Severe symptoms, confusion, fainting, breathing difficulty, chest pain, severe dehydration, or sudden weakness need urgent medical care.
Medicine names, dose, and timing must be decided by a qualified clinician or pharmacist after checking age, pregnancy, allergy, other diseases, and current medicines.

For rural patients and family caregivers

Patient health record and symptom diary

Write your symptoms, medicines already taken, test results, and questions before visiting a doctor. This note stays on your device unless you print or copy it.

Doctor to discuss: Doctor / qualified healthcare provider
Tests to discuss with doctor
  • Basic vital signs: temperature, pulse, blood pressure, oxygen level if needed
  • Relevant blood, urine, imaging, or specialist tests only after clinical assessment
Questions to ask
  • What is the most likely cause of my symptoms?
  • Which warning signs mean I should go to emergency care?
  • Which tests are really needed now?
  • Which medicines are safe for my age, pregnancy status, allergy, kidney/liver/stomach condition, and current medicines?

Emergency warning signs such as chest pain, severe breathing difficulty, sudden weakness, confusion, severe dehydration, major injury, or loss of bladder/bowel control need urgent medical care. Do not wait for online information.

Safe pathway to proper treatment

Care roadmap for: Trapezoid Bone

Use this simple roadmap to understand the next safe steps. It is educational and does not replace examination by a doctor.

Go to emergency care if you notice:
  • Severe or rapidly worsening symptoms
  • Breathing difficulty, chest pain, fainting, confusion, severe weakness, major injury, or severe dehydration
Doctor / service to discuss: Qualified healthcare provider; specialist depends on symptoms and examination.
  1. Step 1

    Check danger signs first

    If danger signs are present, seek emergency care and do not wait for online information.

  2. Step 2

    Record the symptom story

    Write when symptoms started, severity, medicines already taken, allergies, pregnancy status, and test results.

  3. Step 3

    Visit a qualified clinician

    A doctor, nurse, or qualified healthcare provider can examine you and decide which tests or treatment are needed.

  4. Step 4

    Do only useful tests

    Do tests after clinical assessment. Avoid unnecessary tests, random antibiotics, or repeated medicines without diagnosis.

  5. Step 5

    Follow up and return early if worse

    If symptoms worsen, new warning signs appear, or treatment is not helping, return for review quickly.

Rural patient practical tips
  • Take a written symptom diary and all previous prescriptions/test reports.
  • Do not hide medicines already taken, even herbal or over-the-counter medicines.
  • Ask which warning signs mean urgent referral to hospital.

This roadmap is for education. A real diagnosis and treatment plan requires history, examination, and clinical judgment.