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MCP joints of the fingers, Volar plates, Sagittal band of MCP, Collateral…

- - - - Flexion/Extension
      - Abduction/Adduction
      - MCP joint capsule
        
        is lax in extension
        
        allows some passive
        axial rotation of the proximal phalanx
        
        ligaments
        
        2 collateral ligaments
        
        and volar plates present
        
        due to the incongruence
        to stabilize the joint
- - - - Limits hyperxtension
      - Indirectly provide support for the longitudinal arch
      - Composed of fibrocartilage
        
        Able to resist tensile stress
        
        in MCP hyperextension
        
        Able to resist compressive forces
        
        applied on the volar articular surfaces
        
        flexible attachement
        
        Firmly attached to the base of proximal phalanx
        
        but not to the heads of MC
        
        Inner surface of the volar plate is a continuation of the articular surface of the base of the proximal phalanx
        
        Volar plate is can add to the contact surface with the MC head in MCP extension
        
        Allows the plate to glide proximally down on the volar surface of the MC head in
        flexion
        
        without restricting the motion
        
        and prevents pinching of the long flexor tendons in the MCP joints
- - - - the extensor digitorum communis tendon
        
        and extensor expansion
      - Stabilizes the volar plates
        
        over the 4 metacarpal heads
- - - - Lax in MCP extension
        
        and taut in MCP flexion
  - - - and taut in MCP extension
        
        Lax in MCP flexion
- - - - Range of abduction/adduction is maximal in
        
        MCP joint extension
        
        The index and little finger have more frontal plane mobility than 3rd and 4th finger