Acute injuries are caused by a sudden trauma. Common acute injuries among athletes include contusions (bruises), sprains (a partial or complete tear of a ligament), strains (a partial or complete tear of a muscle or tendon) and fractures. But not all injuries are caused by a single, sudden twist, fall, or collision. A series of small injuries can cause minor fractures, minimal muscle tears, or progressive bone deformities, known as overuse injuries.