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.
When the cause of knee swelling is fluid, it's known as knee effusion, or water in the knee.. Contrary to popular belief, the fluid that builds up within the knee is not water. However, the type of fluid depends on the problem. For example, a common cause of water in the knee is gout. Gout is caused by high levels of uric acid. Most knee effusion is caused by the development of a bursa, or a fluid filled sac.