Sprains and strains are common soft tissue athletic injuries. These two terms are often used interchangeably, when in fact each is a distinct injury both in causation and effect.
A sprain is an injury to a ligament, the connective tissue that joins two bones together in a joint. The injury is the result of the ligament fibers being overstretched, often causing a micro-tear, as opposed to the severing or the rupture of the fibers. The overstretching is most often caused by a movement of one beyond the possible range of motion of the joint, either through a hyperextension (overextension), or by a twisting action. Hyper-extended and twisted knees are examples of knee sprains. Ligaments are composed of a type of collagen, which is formed from specific amino acids ingested in the body through dietary protein. Collagen is a naturally elastic substance found in various formations in all of the connective tissue within the body. Collagen provides the overstretched fibers that constitute a ligament sprain with the ability to heal through the action of the body's restorative processes; vitamin C is essential to ligament strength and elasticity.
A strain is an injury that occurs to a muscle or a connecting tendon. A muscle strain is an injury caused to the fibers of skeletal muscle; the other types of muscle, cardiac muscle and smooth organ muscles are not susceptible to strain because they are not controlled by voluntary nervous system impulse. Skeletal muscle is composed of long, thin, cylindrical fibers that are arranged in bundles; a strain is an overstretching or micro-tear of the fiber. Tendons are also formed from a type of collagen, although a tendon is generally a less elastic tissue than a ligament.
Sprains commonly result from a twisting motion in a joint that creates either overextension or over-flexion of the supporting ligaments. A common example of this injury mechanism is a sprained knee caused by contact in sports such as soccer, American football, or rugby. These sprains result from circumstances where the athlete is moving in a forward direction, when the knee is twisted, either through physical contact with an opponent or through a sudden change of direction by the athlete, sometimes accompanied by irregularity or unevenness on the playing surface. The forces that directed the knee forward are suddenly directed laterally, creating torque (a force that causes rotation in the joint), causing the ligaments to stretch. The same mechanism, with a greater degree of force applied, will result in the more serious tear or rupture injury to the ligament.
Another common sprain is to the individual fingers or the wrist, due to an object such as a ball forcefully striking the body and bending the specific structure past its normal range of motion.
A muscle strain, often referred to as a pull, is most often caused by either repetitive motion that overtaxes the muscle, or through an imbalance in a set of muscles. Almost all joints in the body operate through the function of a muscle pair: one muscle, the extensor providing the joint with the ability to extend or straighten, the other, the flexor, permitting the joint to bend. The knee, with the extensor quadriceps and the flexor hamstring is such a joint. A general ideal ratio of strength between the four muscles of the quadriceps and the hamstring is 3:2; muscle and tendon strains are common in both muscle groups when there is an imbalance, which creates additional stress on the weaker of the pair when the forces of motion are applied.
The groin, given its location within the body, is a set of tissues connecting to the abductor muscles of the upper thigh and the lower abdominals, is a common site for a strain injury, as imbalances between the groin and the muscle groups connected to the groin can lead to injury. Groin pulls are very common in sports requiring sudden lateral movement.
Ligament injuries are most often a result of the nature of the physical movement associated with a particular sport, and as such these injuries are not always preventable. Muscle strains are more often caused by a preexisting structural imbalance. A focused and whole body stretching and flexibility regime, where the muscle groups throughout the body are balanced with one another, is the most effective way to minimize muscle and tendon strains.
The overriding goal in the treatment of sprains and strains is the avoidance of a recurring injury. For both injuries, the application of the RICE (rest/ice/compression/elevation) treatment for the first 48 to 72 hours after the occurrence will reduce swelling in the injury and will facilitate healing. Most strains and sprains will not require any external support other than wrapping; crutches may sometimes be necessary when the athlete has sustained a significant strain of a knee or ankle ligament that is short of being torn or ruptured.