Diarthrosis (Synovial) Joint

Authors
Affiliations

Doctor of Physical Therapy

B.S. in Kinesiology

Doctor of Physical Therapy

B.A. in Neuroscience

Characteristics

  • Fluid‐filled joint cavity between bones.
  • “Synovial Joints” – presence of synovial membrane.
  • Designed for movement!

Examples:

  • Majority of Upper and Lower extremity joints.

7 Features

  1. Synovial Fluid
  2. Articular cartilage
  3. Articular capsule
  4. Synovial membrane
  5. Capsular ligaments
  6. Blood vessels
  7. Sensory nerves

Possible Features

Synovial joints may contain:

  • Intraarticular discs / menisci
  • Peripheral labrum
  • Fat Pads
  • Synovial Plicae

Intraarticular discs / menisci

  • Fibrocartilage between surfaces
  • Increase congruency & improve force dispersion

Peripheral labrum

  • Fibrocartilage
  • Deepen concave surface & support capsule

Fat Pads

  • Occupy space within capsular tissue
  • Reduce synovial volume

Synovial Plicae

  • “Pleats” / slack in the synovial membrane.
  • Increase surface area of joint capsule to allow more motion
  • Joints with large capsular surface areas.

Mechanical Classifications

Hinge

  • Flex/Ext
  • Door Hinge

Examples:

  • Humeroulnar
  • IP joints

Pivot

  • Spin
  • Door Knob

Examples:

  • Proximal RU
  • AA joint

Ellipsoid

  • Flex/Ext + Abd/Add
  • Ellipsoid & trough

Examples:

  • Radiocarpal

Ball-and-socket

  • Triplanar
  • Sphere & cup

Examples:

  • GH
  • Hip

Plane

  • Slide, ± Rotation
  • Book on a table

Examples:

  • Intercarpal
  • Intertarsal

Saddle

  • Biplanar
  • Horse rider & saddle

Examples:

  • CMC thumb
  • SC joint

Condyloid

  • Biplanar
  • Abstract parallel: Knuckle & cup

Examples:

  • MCP
  • Tibiofemoral

Citation

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