MCP joints of the fingers

Articulations between the
proximally - convex metacarpal head
distally - concave base of the proximal phalanx

  • Metacarpal heads has 180 degrees of
    articular surface in the
    sagittal plane
  • and predominantly lying on the volar aspect
  • 20 degrees of articular surface
    on the base of the phalanx
  • Incongruent articular surfaces

Condyloid joint

2 degrees of freedom

  • 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

Volar plates

  • Present at each MCP joint
  • to increase joint congruence

Blends and lies deep to the

  • MCP joint capsule and
  • deep transverse metacarpal ligament
    volarly
  • Provides stability for the MCP joints
  • 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

Sagittal band of MCP

  • Dorsal to the
  • deep transverse metacarpal ligament
  • att to Each side of the metacarpal head
  • Connects the volar plates to
  • the extensor digitorum communis tendon
  • and extensor expansion
  • Stabilizes the volar plates
  • over the 4 metacarpal heads

Collateral ligaments of MCP joints

The radial and ulnar collateral ligaments of MCP joints are composed of

Collateral ligament proper

Accessory collateral ligament

  • Dorsally located
  • Lax in MCP extension
  • and taut in MCP flexion
  • Volarly located
  • and taut in MCP extension
  • Lax in MCP flexion

ROM at the MCP joints

Flexion/extension increases

  • radially to ulnarly
  • Index finger - 90 degrees of flexion at MCP
  • little finger -110 degrees of flexion at MCP

Hyperextension

  • is fairly consistent between fingers,
  • but can vary widely among individuals

Range of passive hyperextension has been used as a measure of generalized flexibility

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