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.
Sperm motility describes the ability of sperm to move properly through the female reproductive tract (internal fertilization) or through water (external fertilization) to reach the egg.