Biceps tendon rupture

Your biceps muscle has two tendons at the shoulder — a short head that attaches to a bony bump on the front of the shoulder blade (the coracoid process) and a long head that runs up through a groove in the upper arm bone, over the top of the ball, and anchors to the cartilage rim at the top of the socket (the labrum). A proximal biceps rupture is what happens when the long head — usually weakened by years of tendinopathy — finally gives way.

When the tendon tears, the muscle belly slides down the arm, bunching up in the mid-upper arm and creating the characteristic "Popeye" bulge. The good news is that the short head stays intact, and the short head does most of the heavy lifting for elbow flexion. That means most patients keep reasonable arm strength and actually feel less shoulder pain after the rupture — the chronically inflamed tendon is no longer being pulled through its groove. The tradeoff is a cosmetic deformity and a mild loss of the twisting power you use to turn a screwdriver or open a jar (supination strength).

Most patients describe a sudden pop in the front of the shoulder — sometimes during a lift, sometimes while reaching for something light. The immediate pain can be sharp, but it often settles surprisingly quickly over the first few days (because the tendon that was causing chronic shoulder pain is now gone from the groove). Bruising appears within a day or two, tracking from the front of the shoulder down the inside of the upper arm — sometimes all the way to the elbow.

The Popeye deformity becomes obvious when you flex your elbow: instead of a normal, centered muscle belly, the biceps bunches into a ball lower down the arm. Some patients notice a sense of weakness when twisting a doorknob, using a screwdriver, or carrying heavy bags with the palm up — tasks that load the supination function the long head contributes to. For most people over 50, these functional losses are mild and well-tolerated.

The Popeye deformity itself is usually diagnostic — when your provider asks you to flex your elbow and the muscle bunches asymmetrically compared to the other arm, the diagnosis is clear. Bruising down the upper arm confirms the acute event. Your provider may also perform the hook test — trying to hook a finger under the biceps tendon at the front of the elbow crease. If the tendon can be hooked, the distal tendon (at the elbow) is intact and the rupture is proximal, at the shoulder.

MRI confirms the rupture and — more importantly — evaluates the rotator cuff. In most patients with a proximal biceps rupture, the rotator cuff has been degenerating alongside the biceps for years, and knowing the state of the cuff changes the treatment plan.

Surgical repair (tenodesis) is considered in younger, active patients who require full supination strength, in workers with manual labor demands, and in patients who find the Popeye deformity unacceptable.

External patient-education references and related OSI pages for additional background:

• Britannica — Tendon
• Britannica — Shoulder (anatomy)
• AAOS OrthoInfo — patient education library
• OSI glossary — orthopedic terminology in plain language