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 lubricating fluid called synovial (sih-NO-vee-ul) fluid helps your leg swing smoothly and reduces friction between the moving parts of your knee. But sometimes the knee produces too much synovial fluid, resulting in buildup of fluid in an area on the back of your knee (popliteal bursa), causing a Baker's cyst. This can happen because of: 1  Inflammation of the knee joint, such as occurs with various types of arthritis.  A knee injury, such as a cartilage tear.