Carpal Bones
The carpal bones are eight small bones arranged in two rows that form the wrist. They articulate with each other, the radius, and the metacarpals, allowing complex wrist movements.
Key Features
Articulations
- •Radiocarpal joint (scaphoid, lunate with radius) - condyloid
- •Midcarpal joint (between rows) - compound condyloid
- •Intercarpal joints - plane synovial
- •Carpometacarpal joints (with metacarpals)
Muscle Attachments
Clinical Relevance
Scaphoid fractures are common from falls on outstretched hand and can cause avascular necrosis. The carpal tunnel (bounded by carpal bones and flexor retinaculum) can compress the median nerve. Lunate dislocations can also compress the median nerve.
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Common questions about this bone
A common mnemonic is 'Some Lovers Try Positions That They Can't Handle' for Scaphoid, Lunate, Triquetrum, Pisiform, Trapezium, Trapezoid, Capitate, Hamate (proximal row lateral to medial, then distal row).
The scaphoid spans both carpal rows and receives impact forces during falls on an outstretched hand. Its blood supply enters distally, so proximal fractures can lead to avascular necrosis of the proximal fragment.
The carpal tunnel is a fibro-osseous tunnel formed by the carpal bones and flexor retinaculum. It transmits the median nerve and nine flexor tendons. Compression of the median nerve causes carpal tunnel syndrome.
The trapezium articulates with the first metacarpal of the thumb via a saddle (sellar) joint. This joint allows the thumb's opposition movement, which is essential for grip function.