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.
It can be caused by a problem with the circulatory system, the lymphatic system or the kidneys. You may also experience swelling due to fluid buildup after sitting or standing for a long time. Factors related to fluid buildup include: 1  Acute kidney failure. 2  Cardiomyopathy (disease of heart tissue). 3  Chronic kidney disease. 4  Cirrhosis (scarring of the liver).