[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/) › CMC ligaments [Joints and ligaments](https://durgical.com/en/anatomy/system/joints-and-ligaments/) · [Upper limb](https://durgical.com/en/anatomy/region/upper-limb/) # CMC ligaments The carpometacarpal ligaments join the wrist bones to the palm bones, making the palm a stable arch; the thumb's are looser so it can move. Official name: Carpometacarpal and metacarpal ligaments [See in 3D →](https://durgical.app/?from=durgipedia&lang=en#region=upper_limb&select=cmc_ligs&side=r) Opens in the Durgical app, no sign-up needed. ## What it is Ligaments joining the wrist bones to the bases of the metacarpals and the metacarpals to each other. ## What it does Make the palm a stable arch; the thumb's are looser so it can move. ## Key points - The rigid 2nd and 3rd CMC joints anchor the wrist movers: ECRL inserts on the 2nd metacarpal base, ECRB on the 3rd and FCR on the palmar 2nd - Thumb CMC: the anterior oblique (beak) ligament was long taught as the key restraint; more recent studies favour the dorsoradial ligament against dorsal subluxation (texts differ) - Bennett fracture: a palmar-ulnar fragment stays held by the anterior oblique ligament while APL pulls the 1st metacarpal shaft dorsally and radially, and [adductor pollicis](https://durgical.com/en/anatomy/adductor-pollicis/) adducts it - 5th CMC fracture-dislocation (reverse Bennett): ECU pulls the metacarpal base ulnarly and proximally ## Key facts **Attaches** Distal carpal bones to the metacarpal bases (dorsal, palmar, interosseous); thumb: anterior oblique (beak) and dorsoradial ligaments; intermetacarpal ligaments **Function** Lock the 2nd–3rd CMC joints (fixed central pillar); let the 4th–5th and thumb move **Tight in** Thumb abduction and extension (anterior oblique ligament) ## Relations **In front** [FCR tendon](https://durgical.com/en/anatomy/flexor-carpi-radialis-tendon/) in the groove of the [trapezium](https://durgical.com/en/anatomy/trapezium/) on its way to the [2nd metacarpal](https://durgical.com/en/anatomy/2nd-metacarpal/); the [deep palmar arch](https://durgical.com/en/anatomy/deep-palmar-arch/) and the deep branch of the [ulnar nerve](https://durgical.com/en/anatomy/ulnar-nerve/) across the metacarpal bases **Behind** Insertions of [ECRL](https://durgical.com/en/anatomy/extensor-carpi-radialis-longus/), [ECRB](https://durgical.com/en/anatomy/extensor-carpi-radialis-brevis/) and ECU on the dorsal metacarpal bases; the [extensor tendons](https://durgical.com/en/anatomy/extensor-digitorum-tendons/) to the fingers pass over them **Lateral** [Radial artery](https://durgical.com/en/anatomy/radial-artery/), crossing the back of the first interspace and passing between the heads of the first dorsal interosseous into the palm; APL inserting on the [1st metacarpal](https://durgical.com/en/anatomy/1st-metacarpal/) base ## How to find it Thumb: the base of the first metacarpal stands out on the back of the hand just beyond the radial styloid; the joint line is the groove just proximal to it, which moves when the thumb is circled. Fingers: with the wrist flexed, the bump of the third metacarpal base on the back of the hand marks the 2nd–3rd CMC joints, the usual site of a carpal boss. ## Examination - Grind test of the thumb CMC: axial load with rotation of the 1st metacarpal on the trapezium; pain and crepitus suggest basal thumb osteoarthritis ## On imaging The Robert view (true AP of the thumb base with the hand fully pronated) and a true lateral show trapeziometacarpal arthritis and Bennett fractures. 4th–5th CMC dislocations are easy to miss on the PA view: look for lost parallel joint lines and overlapping bones, and add a pronated oblique view or CT. ## Clinical notes - Basal thumb arthritis is common in older women; laxity of the beak ligament is classically linked to it - Carpal boss: a bony bump on the back of the 2nd–3rd CMC joints, sometimes mistaken for a ganglion - CMC dislocations of the ring and little rays follow punches and high-energy falls and are often missed ## Anatomical variants - An os styloideum, a separate small ossicle at the bases of the 2nd and 3rd metacarpals, may form or enlarge a carpal boss ## Test yourself Think of the answer, then tap the question to see it. ## Which carpometacarpal joints are locked by the CMC ligaments, and why? The 2nd and 3rd, a fixed central pillar that anchors the wrist movers (ECRL, ECRB, FCR); the 4th, 5th and thumb CMC can move. ## In a Bennett fracture, which thumb CMC ligament holds the small fragment? The anterior oblique (beak) ligament holds the palmar-ulnar fragment while APL pulls the shaft dorsally and radially. ## Which test suggests basal thumb osteoarthritis, linked to beak ligament laxity? The grind test: axial load with rotation of the 1st metacarpal on the trapezium; pain and crepitus are positive. ## What deforming force acts in a 5th CMC fracture-dislocation (reverse Bennett)? The ECU pulls the 5th metacarpal base ulnarly and proximally. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/anatomy/carpometacarpal-and-metacarpal-ligaments/) Educational information, not medical advice. For any symptom, see a health professional. ## Its names **Official Latin (TA2)** ligamenta carpometacarpea dorsalia TA2 1828 **Official Spanish (DeCS)** Ligamentos carpometacarpianos y metacarpianos **English (TA2)** Carpometacarpal and metacarpal ligaments ## Related - [Thumb base cartilage](https://durgical.com/en/anatomy/cartilage-of-the-thumb-carpometacarpal-joint/) - [Capitate](https://durgical.com/en/anatomy/capitate/) - [Hamate](https://durgical.com/en/anatomy/hamate/) - [1st metacarpal](https://durgical.com/en/anatomy/1st-metacarpal/) - [2nd metacarpal](https://durgical.com/en/anatomy/2nd-metacarpal/) - [3rd metacarpal](https://durgical.com/en/anatomy/3rd-metacarpal/) - [4th metacarpal](https://durgical.com/en/anatomy/4th-metacarpal/) - [5th metacarpal](https://durgical.com/en/anatomy/5th-metacarpal/) Sources: Terminologia Anatomica (TA2); [Anatomy, Shoulder and Upper Limb, Hand Bones](https://www.ncbi.nlm.nih.gov/books/NBK547684/); Anatomy of the Human Body (20th ed.): Surface Anatomy of the Upper Extremity (Lea & Febiger (Gray's Anatomy, 1918), 1918) · adapted, Public domain. ## **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/carpometacarpal-and-metacarpal-ligaments/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/carpometacarpal-and-metacarpal-ligaments/