Muscle strain

Abstract

Muscle strain is the stretching or tearing of muscle fibers, usually at the musculotendinous junction. Strain occurs when biomechanical forces are in excess of what the muscle-tendon unit can bear. Sometimes strain of the muscle-tendon is the direct result of biomechanical loading of extreme or repetitive forces. At other times the muscle-tendon unit is weak, unable to withstand even small forces. Injuries to the rotator cuff, for example, occur in baseball pitchers following extreme forces, and in the elderly with sarcopenia and degenerating tissues, forces so minor the patient is not able to recall when it happened. Irrespective of person and force, strain launches a body response of pain, swelling, tissue da age, and inflammatory cascade.