Infrapatellar bursitis occurs when one or both of the bursa sacs inside the knee become irritated and inflamed resulting in swelling and knee pain. A bursa is a sac of synovial fluid, rich in protein and collagen.
In biology, motility is the ability of organisms and fluid to move or get around. A microbiologist might test and compare the motility of various single-celled organisms. An easy way to remember that motility means the ability to move without help is the mot- at the root of the word. It's the same root that's found in motor, which is, of course, the engine that drives a car. If you've got good motility then your motor is working.
Cell division is observed in all organisms and is a requirement for reproduction, growth, and development. Many cells also undergo structural changes as they differentiate, such as the outgrowth of axonal and dendritic processes during nerve cell differentiation. A more subtle form of cell motility involves the active transport of membranous organelles within the cytoplasm. This form of movement is required for proper organization of the cytoplasmic contents, and the redistribution of metabolites, hormones, and other materials within the cell.