Microvilli (singular: microvillus) are microscopic cellular membrane protrusions that increase the surface area of cells and minimize any increase in volume, and are involved in a wide variety of functions, including absorption, secretion, cellular adhesion, and mechanotransduction. 1 Locations.
When youâre experiencing back knee pain, the cause of the problem may be due to a condition known as a Bakerâs cyst. When the back knee pain is associated with a Bakerâs cyst, it isnât a cyst in the usual sense. Itâs a popliteal cyst. What this means is that fluid is present in the joint at the back of the knee.
Key points. 1  A popliteal cyst, also known as a Bakerâs cyst, is a fluid-filled swelling that causes a lump at the back of the knee. 2  Common causes of a popliteal cyst include damage to the kneeâs cartilage and rheumatoid arthritis.