What are signs of a proximal bicep tendon rupture?

Pain!: The rupture usually begins with an audible pop followed by severe pain. It can drop you to your knees. Then the "popeye" muscle appears about half way down your arm, since the tendon is no longer able to hold the muscle in place. The pain will gradually fade away but you will be sore for several days.

Weakness: Acutely pain and swelling with some bruising. Patient will have significant weakness of supination of the forearm and some loss of elbow flexion strength. You may see the biceps retract proximally and bunch up in the upper arm , especially with attempted use. This is a surgical problem see a hand surgeon as soon as possible.