Collagen is a natural protein component of the skin that acts like a scaffold and the main building block for cells, tissues and organs. About a third of the protein content in your body is made up of collagen, which is found in the bones, muscles, and tissues of the organs.
1 There can be the accumulation of fluid on the knee after an accident. 2  In most cases, the fluid is blood which can be through a fracture caused to the knee. 3  The swelling of the knee often takes place within some minutes of the injury occurring. 4  Gout and pseudo-gout can also cause fluid on the knee.
The fluid on the knee tends to come and go and varies in amount. There is usually only mild to moderate amounts of swelling. Arthritis is the most common cause of gradual knee swelling, often referred to as water on the knee. Arthritis is the wear and tear of the cartilage and bones. It causes the body to produce extra fluid in the knee, which fluctuates in amounts.