What is the name of the fluid that lubricates joints?

The fluid that lubricates joints is known as synovial fluid. This thick, viscous fluid is produced by the synovial membrane, which lines the joints. Its primary function is to reduce friction between the articular cartilages of synovial joints during movement, thus facilitating smooth joint operation. In addition to lubrication, synovial fluid also provides nutrients to the cartilage and acts as a shock absorber during physical activities.

Serous fluid, produced in serous membranes, helps to reduce friction in body cavities but is not specific to joints. Peritoneal fluid is a type of serous fluid found in the abdominal cavity, serving a different purpose related to internal organs. Fibrin is not a fluid but rather a protein involved in blood clotting. It plays no role in joint lubrication. Understanding the role of synovial fluid is crucial for recognizing how joint function is maintained and the mechanics of movement in horses and other animals.