Joint:Wrist joint:Capsule & ligaments

**Summary**

* Ligaments run obliquely; from periphery to midline; from proximal to distal
* Volar ligaments are key stabilizers; dorsal ligaments, less crucial
* Capitate & lunate have most ligament attachments
* Triquetrum is ulnar anchor for capsular ligaments
* All adjacent carpals have interosseous ligaments: Medial/lateral, distal/proximal (except lunate & capitate - no proximal/distal ligament)

**Volar Radiocarpal Ligaments**

* Radioscaphocapitate (sling, radiocapitate)
	+ Origin: Distal radius, radial styloid; course: Passes across scaphoid waist with minimal attachment; insertion: Capitate body (10% of fibers); arcs around distal lunate, interdigitates with UC & TC to form arcuate ligament
		- Radial collateral: Radial-most fibers of RSC; existence as separate ligament debated
	+ Action: Constrains radiocarpal pronation, ulnocarpal translocation; stabilizes distal scaphoid pole; creates sling for scaphoid
* Long radiolunate (volar radiolunotriquetral, volar radiotriquetral ligament)
* Radioscapholunate (ligament of Testut; intra-articular fat pad)
* Short radiolunate
* Arcuate ("V" ligament): Confluence of ligaments on volar capitate including RSC, UC & TC

**Dorsal Radiocarpal Ligament**

* Dorsal radiocarpal (dorsal radiotriquetral; dorsal radiolunotriquetral)

**Volar Midcarpal Ligaments**

* Scaphotrapezium-trapezoid
* Scaphocapitate
* Triquetrocapitate
* Triquetrohamate
* Pisohamate
* Deltoid: Confluence of scaphocapitate & triquetrocapitate ligaments; parallels arcuate ligament

**Dorsal Midcarpal Ligaments**

* Dorsal intercarpal
	+ Origin: Dorsal triquetrum, interdigitating with DRC ligament; insertion: Scaphoid & dorsal trapezoid
	+ Action: Envelops radial artery in anatomic snuffbox; constrains midcarpal rotation; acts as labrum to capitate head & proximal hamate
* Dorsal scaphotriquetral
	+ Origin: Scaphoid, extending dorsal & distal to SL/LT ligaments; insertion: Dorsal triquetrum
	+ Action: Stabilizes SL/LT ligaments; labrum for capitate head & hamate proximal pole

**Proximal Interosseous Ligaments**

* Scapholunate
	+ Origin/insertion: Ulnar scaphoid to radial lunate; hyaline cartilage attachment
	+ Action: Dorsal portion resists volar-dorsal translation; volar portion limits flexion/extension rotation; proximal accommodates compression & shear forces across radiocarpal joint
	+ U-shaped ligament with dorsal, proximal & volar components
		- Dorsal component thicker (5 mm) than volar (1-2 mm); functionally more important than proximal portion
		- Proximal component is meniscus-like avascular fibrocartilage; triangular shape
	+ Attritional tears with age
* Lunotriquetral
	+ Origin/insertion: Ulnar lunate to radial triquetrum; hyaline cartilage attachment
	+ Action: Volar portion limits translation of lunate & triquetrum; dorsal portion stabilizes joint
	+ U-shaped ligament with dorsal, proximal & volar components
		- Volar component thicker (2.3 mm) than dorsal (1 mm); functionally more important than proximal portion
		- Proximal component is meniscus-like avascular fibrocartilage; triangular shape
	+ Attritional tears with age

**Distal Interosseous Ligaments**

* Trapeziotrapezoid
* Trapeziocapitate
* Capitohamate

**Carpometacarpal Ligaments**

* Pisometacarpal
* Carpometacarpal ligaments of thumb
* Dorsal carpometacarpal
* Volar carpometacarpal

**Distal Radioulnar Ligaments**

* Dorsal radioulnar
	+ Origin: Dorsal sigmoid notch, bone attachment; insertion: Dorsal fibers form ECU sheath & attach to styloid process; volar fibers attach to ulnar fovea
	+ Action: Stabilizes distal ulna, preventing volar subluxation during supination
* Volar radioulnar
	+ Origin: Volar sigmoid notch, bone attachment; insertion: Ulnar fovea; joins with volar fibers of DRU & creates a "ring" (apparent on MR)
	+ Action: Serves as base for UL & UT ligament origins; stabilizes distal ulna, preventing dorsal subluxation during pronation

**Ulnocarpal Structures**

* Ulnolunate
* Ulnotriquetral
	+ Lateral band
	+ Medial band (ulnar collateral ligament)
		- Origin: Arises from DRU at its insertion on ulnar styloid;insertion: Lateral triquetrum
		- Action: Forms floor of ECU tendon sheath; constrains distal translation of triquetrum
		- Actual existence of ulnar collateral ligament is debated
	+ Arises from ligament rather than bone, reducing effects of forearm rotation on carpals
	+ Lateral & medial bands separate just distal to prestyloid recess; lead to pisotriquetral joint (in 90%)
* Ulnocapitate
* Ulnocarpal meniscal homologue

**Triangular fibrocartilage (articular disc)**

* Origin: Arises from radial sigmoid notch, attaching to hyaline cartilage; insertion: Ulnar fovea & styloid tip
* Variable thickness proportional to ulnar length (thicker with ulnar minus, thinner with ulnar plus); ulnar portion 2-3x thicker than radial
* Ulnar portion is vascularized; radial & central portions are not
* Attritional tears with age

* Triangular fibrocartilage complex
	+ Complex includes articular dorsal and volar radioulnar ligament, ulna carpal ligament (UL and UT) & ECU tendon sheath
	+ Action: Transmits portion of axial load from ulnar carpals to distal ulna; stabilizer of DRU joint; stabilizer of ulnar carpals