Muscle strains can occur in any muscle and region of the body and are a result of an overstretching of the involved muscle fibers.

Strains mostly occur during the eccentric portion of a muscular contraction when the muscle is actively lengthening. The forces placed on the muscle exceed the muscles force absorbing capacity which results in tearing of the tissue. Muscle strains are graded based on the amount of muscle torn and range from a Grade I strain which indicates a very mild or minor tearing of the muscle to a Grade III strain which indicates a complete rupture or tear of the muscle and a Grade II strain which is anything in between.  Symptoms include localized pain, stiffness, discolouration and bruising around the strained muscle and a variable loss of function in the muscle depending on the grade of the tear.  Manual therapy and rehabilitation is necessary for the proper management of these conditions.