Distal Biceps Injuries

The biceps muscle runs along the front of the upper arm. At the shoulder, it attaches by two tendons. At the elbow, it attaches by a single tendon with two footprints, the distal biceps tendon, which inserts onto a bony prominence on the radius, one of the two forearm bones, called the radial tuberosity. A broad sheet of tissue called the lacertus fibrosus (bicipital aponeurosis) also extends from the tendon across the front of the forearm and provides additional support.

The distal biceps tendon has two main functions:

• Supination: Rotating the forearm so the palm faces up, as when turning a doorknob, using a screwdriver, or turning a key. The biceps is the most powerful muscle for this motion.
• Elbow flexion: Bending the elbow, as when lifting or carrying an object.

• Complete ruptures: The tendon fully detaches from the bone. If the lacertus fibrosus also tears, the tendon and muscle can retract far up the arm.
• Partial tears: Only part of the tendon is torn, often causing pain and weakness without a visible deformity.
• Tendinopathy: Degeneration and irritation of the tendon from repetitive use, which can weaken the tendon and precede a tear.
• Bicipitoradial bursitis: Inflammation of the fluid-filled sac that cushions the tendon near its attachment, which can cause pain and swelling at the front of the elbow.

Most complete ruptures occur during a sudden, forceful load on a bent elbow while the biceps is contracting, such as catching a falling object, lifting a heavy box, or resisting a strong pull. This type of lengthening contraction places extreme stress on the tendon. Injuries are most common in men between the ages of 30 and 60 and usually affect the dominant arm.

Several factors increase the risk of a distal biceps tear:

• Heavy lifting: Weightlifting, manual labor, and sports that involve sudden loads on the arm.
• Tendon degeneration: Age-related changes and repetitive use weaken the tendon over time.
• Smoking: Nicotine reduces blood flow to tendons and impairs their health.
• Anabolic steroid use: Increases muscle strength beyond what the tendon can tolerate.
• Certain medications: Some medications, including fluoroquinolone antibiotics and corticosteroids, are associated with tendon weakening.

Patients with a complete rupture often describe a distinct pop at the front of the elbow at the moment of injury. Common symptoms include:

• Pain at the front of the elbow: Often sharp at the time of injury and followed by an ache.
• Swelling and bruising: Bruising commonly appears on the front and inner side of the elbow and forearm in the days following the injury.
• Change in the shape of the arm: The biceps muscle may bunch up toward the shoulder, creating a visible bulge and a hollow at the front of the elbow, sometimes called a “reverse Popeye” deformity.
• Weakness turning the forearm: Difficulty with tasks such as turning a doorknob, using a screwdriver, or opening a jar.
• Weakness bending the elbow: Reduced strength lifting and carrying.
• Cramping or fatigue: The biceps may cramp or tire quickly with repetitive use.

Partial tears and tendinopathy usually cause gradually worsening pain at the front of the elbow with lifting and turning the forearm, without a pop or visible deformity.

Diagnosis begins with a detailed history and physical exam. Dr. Rynecki Baker will ask about how the injury occurred, the patient’s occupation and activities, and hand dominance. The exam assesses swelling, bruising, the contour of the biceps muscle, and strength with forearm rotation and elbow bending. Specific maneuvers, including the hook test, in which Dr. Rynecki Baker hooks a finger under the tendon at the front of the elbow, help determine whether the tendon is intact.

Imaging confirms the diagnosis and guides treatment: X-rays rule out fractures and evaluate the bone at the tendon attachment. MRI defines whether the tear is partial or complete, how far the tendon has retracted, and the condition of the tendon and lacertus fibrosus. Ultrasound can provide a quick, dynamic assessment of the tendon in the office.

Timing matters with distal biceps injuries. Once the tendon detaches, it begins to retract and scar within weeks, which can make a direct repair more difficult. Patients who suspect a distal biceps tear should be evaluated promptly so that all treatment options remain available.

Distal biceps injuries require timely, accurate diagnosis and a treatment plan matched to each patient’s goals, whether that means returning to heavy labor, the gym, or elite competition. Dr. Rynecki Baker’s training at NYU Langone Health and Hospital for Special Surgery, including fellowship training in sports medicine and shoulder surgery, and her experience caring for professional athletes on the New York Knicks medical staff, mean patients receive care from a specialist in upper extremity injuries in highly active patients.