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Thumb MCP Joint
- The thumb MCP is similar and different to the digit MCPJ 2-5.
- The CL and articular surface are the same but the volar plate of the thumb contains 2 sesamoid bones and the space between makes a trough for the flexor pollicis longus.
- Ulnar side of the extensor hood is stronger and heavier and formed by the aponeurosis (layers of flat, broad tendons) of the adductor pollicis – this supports the joint against abduction forces
- Radial side of the hood is formed by the tendons of the abductor pollicis brevis and flexor pollicis brevis
- Both sides then blend dorsally with the EPB and EPL
