What describes a sprain?

A sprain specifically refers to an injury involving the ligaments, which are the strong connective tissues that connect bones at a joint. When a sprain occurs, it typically involves the stretching or tearing of a ligament, often due to a sudden twist or impact that forces a joint beyond its normal range of motion. A partial tear of a ligament is a clear definition of what happens during a sprain, which can cause pain, swelling, and limited mobility in the affected joint.

The other options describe different types of injuries: a complete tear of a muscle refers to a muscle strain rather than a sprain; a separation of a tendon involves the attachment between muscle and bone, not ligaments; and a rupture of a joint capsule would involve the protective structure surrounding a joint, but that is not the same as a sprain, which focuses specifically on ligamentous injury. Thus, identifying a sprain as a partial tear of a ligament is the most accurate and clear description.