The biceps brachii muscle is a two-headed muscle that runs along the front of the upper arm, connecting the shoulder and the elbow. Its primary function is to flex the elbow, such as when lifting an object toward the shoulder, and to supinate the forearm, which is the motion used to turn a doorknob or screwdriver. A bicep tear, or rupture, occurs when the tendon that anchors the muscle to the bone is disrupted, separating the muscle fibers from their attachment point. These injuries can range from a partial fraying of the tendon to a complete separation, and the location of the tear significantly affects symptoms and treatment.
Prevalence and Demographics
Biceps tendon ruptures are relatively common upper extremity injuries, though they are disproportionately concentrated in certain demographic groups. The overall incidence of a complete distal biceps tendon rupture (at the elbow) is estimated to be around 1.2 to 2.55 cases per 100,000 patient-years. This rate has been trending upward, likely due to an increasingly active aging population.
The vast majority of all biceps ruptures—approximately 96%—occur at the shoulder, involving the long head of the biceps tendon. Proximal tears are much more frequent, but distal tears often present a greater functional concern. Proximal tears are frequently seen in older patients as a result of chronic wear and tear over time.
The population most affected by distal biceps ruptures consists overwhelmingly of middle-aged men, often between 35 and 54 years old. More than 95% of patients presenting with this injury are male, and the tear commonly involves the dominant arm. These injuries are often associated with activities that involve sudden, heavy resistance, such as manual labor, weightlifting, or attempting to catch a heavy, falling object.
Distinguishing Between Tear Locations
The biceps muscle has two tendons that attach it to the shoulder (proximal) and one tendon that attaches it to the forearm bone at the elbow (distal). The long head of the biceps tendon is the most frequently injured tendon, located at the shoulder joint.
A rupture of this long head tendon at the shoulder typically results in a cosmetic deformity known as the “Popeye” muscle sign. This involves the detached muscle belly retracting down the arm, creating a noticeable bulge in the lower part of the upper arm and a corresponding gap near the shoulder. Because the short head tendon remains intact, most patients retain reasonable elbow function, experiencing only mild weakness.
In contrast, a tear of the distal biceps tendon occurs when the single tendon is pulled away from its insertion point on the radius bone near the elbow. This injury is characterized by severe pain and significant bruising that often extends down the forearm. The physical presentation may include a palpable gap or indentation in the front of the elbow.
The functional impact of a distal tear is substantially greater because the biceps is the primary muscle for forearm supination. Without its attachment, patients experience a considerable loss of strength in both elbow flexion and, most notably, forearm rotation.
Primary Causes and Contributing Factors
Biceps tears are generally categorized into two main mechanisms: acute trauma and chronic degeneration. Acute traumatic tears occur when a sudden, unexpected load is placed on the muscle, usually involving an eccentric contraction. This happens when the muscle is contracting while simultaneously being forced to lengthen, such as when lowering an extremely heavy weight or resisting a forceful hyperextension of the elbow.
The more common cause, particularly for proximal tears at the shoulder, is chronic degeneration, or tendinopathy. Over time, repetitive motion and age-related wear cause the tendon fibers to fray and weaken. This progressive damage makes the tendon susceptible to a complete tear even with a relatively minor force.
Age is a significant factor, as tendons naturally become less elastic and robust after the age of 40. Smoking is a well-documented risk factor, with nicotine exposure potentially increasing the risk of a distal biceps tendon rupture by as much as 7.5 times. Other systemic factors include the use of corticosteroid medications and an elevated body mass index (BMI).
Pre-existing conditions in the shoulder, such as rotator cuff tears or shoulder impingement, can also place greater stress on the biceps tendon. This stress accelerates the tendon’s degeneration and predisposing it to rupture.
Immediate Steps and When to See a Doctor
If a person suspects a biceps tear, the immediate priority is to minimize pain and swelling and prevent further injury. The RICE protocol is the standard initial first aid: Rest the arm and apply Ice to the affected area for 15 to 20 minutes several times a day to reduce swelling. Over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs) can be taken to manage pain and inflammation.
While most proximal tears can be managed without surgery, a proper diagnosis is necessary to determine the extent of the injury and the appropriate course of action. A medical consultation is necessary when symptoms include a sudden, sharp pain accompanied by an audible “pop” or snapping sensation.
Immediate evaluation by a physician is warranted if there is a visible deformity, such as the muscle bulge or a gap near the elbow. Severe weakness, especially the inability to rotate the forearm (supinate) against resistance, is a strong indicator of a complete tear. Distal biceps tendon ruptures are considered time-sensitive injuries because surgical repair is often recommended within the first few weeks to prevent the tendon from retracting and scarring.