Musculocutaneous nerve damage is an uncommon but important cause of weakness and sensory changes in the arm. In sporting contexts, it is most often related to trauma, overstretching, or entrapment of the nerve during high-demand activities. The musculocutaneous nerve supplies the biceps, brachialis, and coracobrachialis muscles, and also provides sensation to the lateral forearm. When injured, athletes may present with both motor and sensory symptoms that can significantly impair performance. Recognising the features of a musculocutaneous nerve injury is essential to avoid misdiagnosis, as it can mimic conditions such as biceps tendon rupture, cervical radiculopathy, or brachial plexus injury.

Symptoms of Musculocutaneous Nerve Damage

Athletes with musculocutaneous nerve injury usually describe weakness in elbow flexion, particularly when trying to lift or carry objects. There may be a loss of power during sporting activities such as throwing, tackling, or weight training. Many patients also report numbness, tingling, or altered sensation along the outer (lateral) part of the forearm. Pain may or may not be present, but when it occurs, it is often felt in the upper arm or shoulder following a traumatic episode such as a direct blow, shoulder dislocation, or overstretching during contact sport.

Clinical Presentation

On examination, there is typically weakness in elbow flexion due to reduced function of the biceps and brachialis muscles. Supination of the forearm may also be weaker than expected.

Sensory loss or altered sensation is often found along the outer border of the forearm, which is supplied by the lateral cutaneous nerve of the forearm, a branch of the musculocutaneous nerve. The shoulder itself may appear normal, but signs of associated trauma, such as bruising, swelling, or a history of shoulder dislocation, are important clues. Unlike biceps tendon rupture, there is no “Popeye” sign, and neck movements do not usually reproduce symptoms.

Other possible causes doctors need to exclude include biceps tendon ruptures, nerve pinching from the neck and acute brachial neuritis. 

Investigations

Investigations help confirm the diagnosis and rule out other causes of arm weakness and sensory change.

  • Electromyography (EMG) and nerve conduction studies are the gold standard, demonstrating reduced conduction velocity or absent signals in the musculocutaneous nerve distribution.

  • MRI of the brachial plexus or shoulder may be required if entrapment, scarring, or structural injury is suspected.

  • Ultrasound can help exclude biceps tendon rupture and visualise nerve continuity or swelling.

Treatment of Musculocutaneous Nerve Damage 

Most cases of musculocutaneous nerve damage improve with conservative management. Treatment includes:

  • Rest and activity modification to avoid further traction or compression of the nerve.

  • Physiotherapy focuses on maintaining shoulder and elbow mobility while strengthening other muscle groups.

  • Neuromuscular rehabilitation to encourage nerve recovery. 

  • Pain control with NSAIDs or nerve pain medication (amitriptyline or duloxetine) if symptoms are persistent.

  • Surgical intervention may be considered if there is no improvement after six months, particularly when nerve entrapment, laceration, or scarring is demonstrated on imaging. Microsurgical nerve repair or grafting may restore function in selected cases.

Final Word from Sportdoctorlondon regarding Musculocutaneous Nerve Injury

Musculocutaneous nerve injury in sport is rare but can cause significant weakness in elbow flexion and altered sensation along the lateral forearm. It is most commonly seen after trauma, traction, or shoulder dislocation. Diagnosis is confirmed with nerve conduction studies and imaging, while treatment is usually conservative with physiotherapy and activity modification. Surgical repair may be required in severe cases. Early recognition of musculocutaneous nerve damage is essential to optimise recovery and help athletes return to sport safely.