Ligaments are strong bands of fibrous tissue that connect bone to bone, and often play an important stabilizing role in a joint. Most sprained ankles happen when the outer, or lateral, ligaments are stretched too much. Sprains are graded based on their severity, ranging from a strain (mild), to a partial tear (moderate), to a complete tear (severe). Lateral ankle sprains can damage the ankle joint and limit your mobility. Without treatment, recurrent sprains can occur, causing chronic problems with the ankle.