Abrasion: the wearing away of something, as happens to skin when it gets scraped.
Anterior cruciate ligament (ACL): 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.
Achilles tendon: a band of tissue that connects muscles to the heel bone.
Acute: a rapidly developing condition. An acute medical condition comes on quickly and often causes severe symptoms, but lasts only a short time.
Acute traumatic injury: in sports, these injuries usually involve a single blow from a single application of force, like getting a cross-body block in football.
Buckle or torus fracture: when one side of the bone bends, raising a little buckle, without breaking the other side.
Chronic: 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.
Chronic injury: 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.
Closed fracture: a fracture that doesn't break the skin.
Comminuted fracture: when the bone is broken in more than two pieces or crushed.
Computed tomography (CAT): also called computed tomography scan or CT scan. This is a type of X-ray in which a machine rotates around the patient and creates a picture of the inside of the body from different angles. Regular X-rays show bones and other areas of the body, but CAT scans show much more detail.
Concussion: a temporary loss of normal brain function.
Contusion: a bruise caused by a direct blow, which may cause swelling and bleeding in muscles and other body tissues.
Corticosteroids: medications that doctors prescribe to treat some illnesses or injuries. For example, corticosteroids can be used to reduce or prevent swelling and irritation (like asthma control medications or anti-itch creams). Not to be confused with anabolic steroids.
Delayed onset muscle soreness: describes pain or soreness felt hours or days after exercise.
Displaced fracture: a fracture in which the pieces on either side the break are out of line. This type of fracture might require surgery to make sure the bones are properly aligned before casting.
Epiphysitis or apophysitis: growth plate overload injuries such as Osgood-Schlatter disease.
Fracture: a crack, break, or shattering of the bone.
Flexibility: the range of motion possible around specific joints — the ability to move muscles and joint through their full range of motion.
Greenstick fracture: a partial break in which one side of the bone is broken and the other side bends (this fracture resembles what would happen if you tried to break a green stick).
Hairline fracture: a thin break in the bone.
Hematoma: a bleeding or pooling of blood in an organ or other area of the body, usually because of a broken blood vessel.
Laceration: a cut in the skin that is usually deep enough to require stitches.
Ligament: tough fibrous tissue that connects a bone to another bone to form a joint.
Magnetic resonance imaging (MRI): a safe and painless test that uses a magnetic field and radio waves to produce detailed pictures of the body's organs and structures.
Medial collateral ligament (MCL): a ligament that helps give the knee stability — one of the four main ligaments in the knee joint that connect it to the shinbone and thighbone.
Medical history: information about a person's past health, their family's health, and other issues.
Muscle: masses of tough, elastic tissue that pull bones when during movement.
Muscle cramp: involuntary spasm or contraction in one or more muscles.
Non-displaced fracture: a fracture in which the pieces on either side of the break line up.
Range of motion: the extent to which a joint can be extended and flexed in a normal way. Doctors use this to evaluate joint injuries.
Repetitive stress injuries (RSIs): injuries that happen when too much stress is placed on a part of the body, resulting in inflammation (pain and swelling), muscle strain, or tissue damage.
Risk factor: something that increases the chance of illness or injury (running in bad shoes, for example).
Segmental break or fracture: when the same bone is broken in two or more places.
Single fracture: when a bone is broken in one place.
Sprain: a stretch or tear of a ligament, the tissue that supports and strengthens joints by connecting bones and cartilage.
Steroids (anabolic): artificially produced hormones that are the same as or similar to androgens, the male sex hormones in the body.
Strain: a stretch or tear of a muscle or tendon, the tough and narrow end of a muscle that connects it to a bone.
Stress fractures: tiny cracks in the bone's surface often caused by repetitive overloading (such as in the feet of a basketball player who is continuously jumping on the court).
Tear: where tissue is pulled or ripped apart by force.
Tendinitis: inflammation of the tendon caused by repetitive stretching.
Tendon: a band of tissue that connects muscle and bone.
Ultrasound: a way for doctors to take a look inside the body. Instead of X-rays, soundwaves are bounced off the kidneys, the heart, or other areas of the body.
Whiplash: an injury to the neck caused by an abrupt jerking motion of the head.
X-ray: a procedure that uses radiation to take pictures of internal areas of the body. They're done by an X-ray technician in the radiology department of a hospital, a freestanding radiology center, or a health care provider's office.