Which term describes a freely movable joint such as the shoulder?

Which term describes a freely movable joint such as the shoulder?

• A. Diarthrosis
• B. Synarthrosis
• C. Amphiarthrosis
• D. Synostosis

Answer: (A)

Movable joints are diarthroses, the most mobile category of joints. They’re synovial joints with a fluid-filled joint cavity, articular cartilage on the ends of bones, a fibrous joint capsule reinforced by ligaments, and often bursae or tendon sheaths to reduce friction. The shoulder exemplifies this because it’s a ball-and-socket synovial joint that allows movement in many directions and rotation. That level of freedom is what defines a diarthrosis. In contrast, synarthroses are immovable joints (like skull sutures), amphiarthroses are slightly movable (such as the pubic symphysis or intervertebral joints), and synostosis refers to a joint that has fused into a single bone with no movement. So the freely movable shoulder best fits diarthrosis.

Movable joints are diarthroses, the most mobile category of joints. They’re synovial joints with a fluid-filled joint cavity, articular cartilage on the ends of bones, a fibrous joint capsule reinforced by ligaments, and often bursae or tendon sheaths to reduce friction. The shoulder exemplifies this because it’s a ball-and-socket synovial joint that allows movement in many directions and rotation. That level of freedom is what defines a diarthrosis. In contrast, synarthroses are immovable joints (like skull sutures), amphiarthroses are slightly movable (such as the pubic symphysis or intervertebral joints), and synostosis refers to a joint that has fused into a single bone with no movement. So the freely movable shoulder best fits diarthrosis.