The biceps tendon, the strong tissue that connects the biceps muscle to the bone can become avulsed or torn away as the result of a trauma. There are two types of avulsions that can happen: the proximal avulsion (close to the shoulder) or the distal avulsion, closer to the elbow.
The typical patient with a biceps tendon rupture is a male, over 35 to 40 years old, who do strength type exercises, body building, or heavy lifting. The tendon will snap, sometimes causing a snapping sound that the patient can hear. It doesn't usually happen all of a sudden, but to a tendon that is already injured or prone to injury.
Someone with a snapped biceps tendon will likely have bruising and swelling, and the muscle will look unnaturally bunched up or cramped.