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.
White blood cells, such as neutrophils and macrophages must quickly migrate to sites of infection or injury to fight bacteria and other germs. Cell motility is a fundamental aspect of form generation (morphogenesis) in the construction of tissues, organs and the determination of cell shape.