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.
A: Fluid buildup can occur after a knee replacement because of infection, according to Healthline. This can result in aspiration or drainage of the fluid or revision surgery to correct the problem. Sometimes infection occurs in the new replacement joint after surgery, resulting in fluid buildup, swelling and tenderness, states Healthline.