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.
Fluid Outside The Knee Joint. When fluid is outside of the actual joint space, and in the soft tissues surrounding the knee, the most common cause is prepatellar bursitis. This condition causes fluid accumulation in the bursa just on top of the kneecap. Usually, the fluid can be felt on top of the kneecap, rather than underneath the kneecap.