[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Anatomy](https://durgical.com/en/anatomy/) › [Upper limb](https://durgical.com/en/anatomy/region/upper-limb/) › 3rd metacarpal [Skeletal system](https://durgical.com/en/anatomy/system/skeletal-system/) · [Upper limb](https://durgical.com/en/anatomy/region/upper-limb/) # 3rd metacarpal The third metacarpal is the palm bone of the middle finger; it forms the stable centre of the palm and anchors a main wrist extensor. [See in 3D →](https://durgical.app/?from=durgipedia&lang=en#region=upper_limb&select=metacarpal_3&side=r) Opens in the Durgical app, no sign-up needed. ## What it is The long bone in the palm leading to the middle finger. ## What it does Forms the palm and the knuckle at its head. ## Key points - The only metacarpal with a styloid process on the back of its base, where the ECRB inserts - Its head is the most prominent knuckle; the [axis](https://durgical.com/en/anatomy/axis/) of the hand passes through the middle finger, so finger abduction and adduction are described relative to it - Its carpometacarpal joint with the capitate is almost immobile, part of the hand's fixed central pillar ## Key facts **Joints with** Base: capitate; head: proximal phalanx; adjacent metacarpals **Landmarks** Base, shaft, neck, head (knuckle) ## Relations **Above** [Capitate](https://durgical.com/en/anatomy/capitate/) **Behind** [ECRB](https://durgical.com/en/anatomy/extensor-carpi-radialis-brevis/) on the styloid process; [extensor digitorum](https://durgical.com/en/anatomy/extensor-digitorum/) tendon to the middle finger **In front** Transverse and oblique heads of the [adductor pollicis](https://durgical.com/en/anatomy/adductor-pollicis/); the [deep palmar arch](https://durgical.com/en/anatomy/deep-palmar-arch/) near its base **Lateral** Second dorsal interosseous **Medial** Third dorsal interosseous **Below** [Proximal phalanx of the middle finger](https://durgical.com/en/anatomy/proximal-phalanx-of-the-middle-finger/) ## How to find it The styloid process is felt as a small bump at the base of the 3rd metacarpal on the back of the hand, just distal to the capitate, more obvious with the wrist flexed; the head is the most prominent knuckle of a fist. ## On imaging Seen on PA, oblique and lateral hand views. The styloid process sits on the dorsal radial corner of its base; a separate small bone there (os styloideum) or a bony bump (carpal boss) is best shown on a lateral view and should not be read as a fracture. CT clarifies complex CMC injuries; ultrasound shows a ganglion over a carpal boss. ## Clinical notes - A prominent styloid or an osteophyte here forms the carpal boss, which can be confused with a dorsal wrist ganglion - Shaft fractures of this central metacarpal shorten little, because the deep transverse metacarpal ligaments tie its head to the neighbouring heads on both sides - Fracture-dislocations at its carpometacarpal joint are rare and need high energy, since the joint with the capitate is locked by strong ligaments ## Anatomical variants - Os styloideum: an accessory ossicle at the base, in place of a fused styloid process ## Development Ossifies in cartilage: a primary centre appears in the shaft before birth and one secondary centre later forms at the head, not at the base as in the [1st metacarpal](https://durgical.com/en/anatomy/1st-metacarpal/). On a child's X-ray the open plate near the head shows as a dark line that is easy to mistake for a fracture. ## Related conditions - [Trigger finger](https://durgical.com/en/conditions/trigger-finger/) ## Test yourself Think of the answer, then tap the question to see it. ## Which metacarpal has a styloid process, and what inserts on it? The 3rd metacarpal; the extensor carpi radialis brevis inserts on its styloid process. ## Why are finger abduction and adduction described relative to the 3rd metacarpal and middle finger? The axis of the hand passes through the middle finger. ## What forms a carpal boss at the 3rd metacarpal base? A prominent styloid process or an osteophyte, which can be confused with a dorsal wrist ganglion. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/anatomy/3rd-metacarpal/) Educational information, not medical advice. For any symptom, see a health professional. ## Its names **Official Latin (TA2)** ossa metacarpi TA2 1264 **Official Spanish (DeCS)** Hueso metacarpiano III **English (TA2)** 3rd metacarpal ## Related - [A1 pulleys](https://durgical.com/en/anatomy/a1-pulleys-of-the-flexor-tendon-sheaths/) - [Adductor pollicis](https://durgical.com/en/anatomy/adductor-pollicis/) - [CMC ligaments](https://durgical.com/en/anatomy/carpometacarpal-and-metacarpal-ligaments/) - [Dorsal interossei](https://durgical.com/en/anatomy/dorsal-interossei/) - [ECRB](https://durgical.com/en/anatomy/extensor-carpi-radialis-brevis/) - [Extensor tendons](https://durgical.com/en/anatomy/extensor-digitorum-tendons/) - [Finger joint capsules](https://durgical.com/en/anatomy/finger-joint-capsules/) - [Lumbricals](https://durgical.com/en/anatomy/lumbricals/) Sources: Terminologia Anatomica (TA2); [Anatomy, Shoulder and Upper Limb, Hand Bones](https://www.ncbi.nlm.nih.gov/books/NBK547684/); [8.5 Development of the Appendicular Skeleton](https://openstax.org/books/anatomy-and-physiology-2e/pages/8-5-development-of-the-appendicular-skeleton) (OpenStax (Rice University), 2022) · adapted, [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/anatomy/3rd-metacarpal/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/3rd-metacarpal/