Interphalangeal joints (IP)

• Joint Classification:

  • Synovial hinge joints
• Axis of movement:

  • One degree of freedom: transverse axis
• Articular Surfaces:

  • Head of proximal phalanx with base of middle phalanx

  • Head of middle phalanx with base of distal phalanx

  • Covered in hyaline cartilage

  • Fibro-cartilaginous plate present known as palmar ligament (increases articular area of base of adjacent phalanx)
• Joint Capsule:

  • Loose fibrous capsule

  • Strengthened laterally by collateral ligaments

  • Replaced by palmar ligament anteriorly
• Ligaments:

  • Collateral ligaments: Attach to sides of head of most proximal phalanx to sides of base of adjacent phalanx. Tension increases during flexion.
• Ligaments:

  • Palmar ligaments: Fibro - cartilaginous plate increasing surface area of base of adjacent phalanx. Limit extension.
• Movements:

  • Flexion = 90 -135° (increasing towards the little finger)

  • Extension = 1- 5°