Muscles, tendons and bones comprise units. These units stabilize the foot and allow its motion. A strain occurs at the weakest part of a unit. There is no loss of strength. Strength is diminished.
Severe strain requires surgical repair.
Chronic strains are caused by overuse. Acute strains are caused by direct injury or overstress. Tendons and muscles of the foot. Pain when moving or stretching the foot. Muscle spasm in the foot.