Ruptured Muscle

A ruptured muscle in the leg is usually a big problem.
It's difficult to walk with a ruptured Achilles or patellar tendon

Ruptured muscles in the arm can be more subtle

Note the more prominent muscle on the injured side (arrow). Most of the muscle in this area is the brachialis, not the biceps.

Note the more prominent muscle on the injured side (arrow). Most of the muscle in this area is the brachialis, not the biceps.

Proximal Biceps Rupture:

Rupture of the long head of the biceps at the shoulder makes the arm muscle look bigger.

There is no loss of function because the muscle has another attachment at the shoulder. 

Surgery is not needed.

Proximal biceps rupture is part of rotator cuff degeneration.

Distal biceps rupture usually presents as pain and bruising after a pop when the arm was forcibly straightened. There is often less deformity than with proximal biceps rupture

Distal biceps rupture usually presents as pain and bruising after a pop when the arm was forcibly straightened. There is often less deformity than with proximal biceps rupture

Distal Biceps Rupture:

Middle aged man

Arm straightened while trying to flex

Loss of supination strength

Flexion strength is fine because the brachialis muscle is still working

Surgery to reattach the muscle is for 30% stronger supination (twisting the lower arm). 

Flexion strength is near normal with or without surgery