the wearing away of something, as happens to skin when it gets scraped.

a ligament that helps give the knee stability — one of the four main ligaments in the knee joint that connect to the shinbone and thighbone.

a band of tissue that connects muscles to the heel bone.

a rapidly developing condition. An acute medical condition comes on quickly and often causes severe symptoms, but lasts only a short time.

in sports, these injuries usually involve a single blow from a single application of force, like getting a cross-body block in football.

when one side of the bone bends, raising a little buckle, without breaking the other side.

a condition that someone has for a long time or one that goes away and keeps coming back. Diabetes and juvenile rheumatoid arthritis, for example, are chronic illnesses.

An injury that happens over a period of time and is usually the result of repetitive training, such as running, overhand throwing, or serving a ball in tennis.

a fracture that doesn't break the skin.

when the bone is broken in more than two pieces or crushed.