Muscles, tendons and attached bones comprise units. These units stabilize the wrist 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 forearm. Bones at the wrist, where the muscles and tendons attach. Pain when moving or stretching the wrist.