1st Carpometacarpal Joint (CMC)

• Joint Classification:

  • Synovial Saddle joint
• Axis of movement:

  • Varies
• Articular Surfaces:

  • Trapezium (convex medial to lateral/ concave palmar to dorsal)

  • Base of 1st metacarpal (MC) is reciprocal

  • Surfaces covered in hyaline cartilage
• Joint Capsule:

  • Loose but strong, attaching to articular margins

  • Thickened by radial carpometacarpal ligament (laterally) and anterior and posterior oblique ligaments (anteriorly/posteriorly)
• Ligaments:

  Radial carpometacarpal ligament

  • Lateral adjacent surfaces of trapezium and 1st MC

  • Role: Reinforce capsule and stabilise joint
• Ligaments:

  Anterior and posterior oblique ligaments

  • From anterior/posterior surface of trapezium (respectively) to medial side of 1st MC (merging on route)

  • Role: Limits flexion (posterior ligament) and extension (anterior ligament)
• Flexion/extension:

  • Total ROM: 40-50 Abduction/adduction:

  • Total ROM: 80 Opposition:

  • Phase 1: abduction

  • Phase 2: flexion and medial rotation

  • Phase 3: adduction (depending on where it wants to go, i.e. to a finger or part of palm)