Diarthrosis (Synovial) Joint

Authors

Affiliations

Nate Yomogida, B.S., SPT

Doctor of Physical Therapy

B.S. in Kinesiology

Chloë Kerstein, B.S., SPT

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