A muscle strain is an injury to a muscle or tendon. Minor injuries may affect only a muscle or tendon, while more severe injuries may involve partial or complete damage to these tissues. Strains can occur in any muscle, but are most common in the lower back, neck, shoulder and thigh, which is the muscle behind your thigh. To simplify diagnosis and treatment, we will classify Muscle Strains into three grades, depending on the severity of the muscle fiber damage:

Grade I. In this mild strain, only a few muscle fibers are stretched or torn. Although the injured muscle is tender and painful, it has normal strength.

Grade II. This is a moderate stretch with a greater number of injured fibers and more severe muscle pain and tenderness. There is also mild swelling, a visible loss of strength and sometimes bruising.

Grade III. This tightness tears the muscle all the way through, sometimes causing a twitching sensation as the muscle breaks into two separate pieces or pulls away from its tendon. Grade III strains are serious injuries that cause complete loss of muscle function, as well as considerable pain, swelling, stiffness and pallor.