What is the difference between a sprain, a strain, and a tear?

Actually, these terms all pretty much .refer to the same Process occurring in different structures. When ligaments are injured or torn, we speak of this process as a "sprain". When tendons are injured, we call this a "strain". Muscle injuries are referred to as "muscle tears" or sometimes as muscle "strains".

What is the difference between a muscle, a tendon, and a ligament?

Muscles are tissues which contract and thereby cause motion across a joint. For example, contracting the biceps causes the elbow to flex. Contracting the gastrocnemius causes the foot to plantar flex (point downward). Tendons are cord-like or strap-like continuations of muscles which attach the muscles to the bones. Ligaments connect bone to bone without any contracting portion and thereby provide stability and alignment.

How does an injury occur?

Sometimes, a sudden force or load is applied to a structure and a frank tear occurs. Often, however; this is not the case at all. Rather; overuse of the structure (a relatiw mismatch of load to capacity), results in microtrauma (microscopic injury to the structure). Only after numerous repetitive microtears occur will the individual perceive that the structure has indeed sustained an injury.

What is the natural course of a sprain, strain, or tear?

In most cases, these injuries do not result in permanent damage or dysfunction of the underlying structures. Unless there is a virtually complete tear of muscle, tendon, or ligament, the involved joints will not be unstable and the, tissues will ultimately heal to a greater or lesser extent. The initial response of the body is one of inflammation, swelling, and pain. This results in muscle spasm in surrounding tissues to "splint" or protect the region against further motion which might extend or worsen the injury. The involved and nearby muscles tend to shorten and weaken if the injury is moderately severe and the spasm and inflammation are prolonged.

What is inflammation?

Inflammation is the body's normal response to any insult or injury. The body receives a "signal" that tissue has been damaged and sends specific cells and chemicals to that site. Some of the chemicals produce pain. This pain is a signal to the person that something has happened and serves to help the person protect himself from further injury. These chemicals also produce swelling: the swelling is part of the inflammatory process which promotes increased circulation and metabolism in the injured area. This allows the cells to break down the injured tissue and. "clean up" the debris. It also allows for production of new ligament, tendon, or muscle tissue to substitute and replace the injured tissue. The surrounding muscles are signaled to contract involuntarily and protect -the region from undue motion in order to reduce the risk of further injury. The inflammatory response is a complex one which is still being very vigorously studied and elucidated by on going research. Although inflammation is vital for repair of injured tissue, often the process will continue beyond being beneficial and will act to the detriment of the healing process.