Final answer:
Synovial fluid is the name of the fluid contained in joint capsules. It lubricates the joints and reduces friction between the bones, allowing for smooth movement.
Step-by-step explanation:
The name of the fluid contained in joint capsules is synovial fluid. Synovial fluid is a lubricating fluid found within synovial joints, which are the most common type of joints in the body. It helps reduce friction between the bones and allows for smooth movement.