A muscle injury is an injury to a muscle or tendon, which can be caused by overuse, trauma, or STRAIN. A TEAR is a type of muscle injury where the muscle fibers are torn, usually due to a sudden movement or force. A STRAIN is an injury to a muscle or tendon caused by overstretching or over-contracting the muscle. A SPRAIN is an injury to a ligament, which is a band of tissue that connects two bones together. Sprains are usually caused by a sudden twist or turn of the joint.