Joints are the connection between two or more bones. Mobile joints are referred to as which?

• A. Diarthroses or synovial joints
• B. Fibrous sutures
• C. Synarthroses
• D. Cartilaginous joints

Answer: (A)

The amount of movement a joint allows defines its class. Joints that move freely are called diarthroses, and when described anatomically they are known as synovial joints. This pair of terms refers to joints with a joint cavity, articular cartilage, a synovial membrane producing lubricating fluid, and a fibrous capsule and ligaments that together enable a wide range of motion. That combination of features is what makes them the mobile category.

Understanding the contrast helps: fibrous sutures are immovable connections between skull bones, so they’re not mobile. Synarthroses is the term for immovable joints. Cartilaginous joints can be immovable or only slightly movable, so they aren’t automatically considered freely mobile. So the best way to describe joints that are mobile is diarthroses, also called synovial joints.