Hand Anatomy and Joint Movements

Overview of Hand Joints

• Hand has multiple joints.
• Key bones and joints:
  • Capitate: Third (middle) finger.
  • Metacarpal bone forms CMC joint with capitate.
  • Proximal phalanx forms MCP joint with metacarpal bone.
  • PIP and DIP joints.

Carpometacarpal (CMC) Joints

• CMC Joint: Carpometacarpal joints.
• Mobility varies:
  • 2nd & 3rd CMC: Less mobile.
  • Thumb CMC: More mobile, important for grip and thumb movement.
  • 4th & 5th CMC: More mobile compared to 2nd & 3rd.

Thumb CMC Motion

• Saddle joint: Allows various thumb movements.
• Terminology can be confusing:
  • Palmar Abduction: Thumb moves up pointing to the ceiling.
  • Radial Abduction (Extension): Thumb moves outward or away.
  • Adduction: Thumb moves back from radial abduction.
  • CMC Flexion: Thumb bends inward trying to touch the hand.
  • Opposition: Thumb's pad touches the pad of little, ring, middle, or index finger.

Metacarpophalangeal (MCP) Joints

• MCP Joints: Consist of convex and concave joint surfaces.
• Stability: Depends on collateral ligaments.
  • Radial Collateral Ligament: Radial side support.
  • Ulnar Collateral Ligament: Ulnar side support.
• Important points:
  • Ligaments are tight when MCP joint is flexed at 90°.
  • Injuries and swelling can prevent bending, leading to ligament loosening over time.
  • Essential for fine motor skills and object manipulation.
  • Collateral ligaments are necessary for the stability of the joint.
  • Positioning the MCP in 90° flexion post-injury to avoid long-term complications.

Interphalangeal (IP) Joints

• Each finger has two IP joints:
  • Proximal Interphalangeal (PIP) Joint.
  • Distal Interphalangeal (DIP) Joint.
• Thumb has one IP joint.
• Movement: Allows flexion and extension only.
• Stability: Depends on collateral ligaments.