Shoulder movement is something most people take for granted. Reaching for something on a high shelf, lifting a bag or rotating to look behind you are some of the movements that feel automatic until they are not. An axillary nerve injury can disrupt all of it, and it does not always make itself obvious right after a trauma.

The axillary nerve runs from the C5 and C6 nerve roots in your neck through the back of the shoulder, where it controls the deltoid and teres minor muscles. Those two muscles are responsible for lifting the arm out to the side and rotating it outward. The nerve also carries sensation to the outer upper arm and shoulder.

Symptoms of Axillary Nerve Injury

The most common complaint is weakness when trying to lift the arm out to the side. Patients often describe the arm as just not responding the way it should. You may also notice the following:

• Weakness when rotating the arm outward
• Numbness or tingling along the outer shoulder and upper arm
• Shoulder pain that came on with a fall or dislocation

In cases where the deltoid weakens over time, the shoulder’s normal rounded shape can begin to flatten.

An axillary nerve injury overlaps with rotator cuff problems and other shoulder issues, which is part of why nerve injuries get missed. If your shoulder feels weak and numb together after a trauma, tell your physician specifically.

Causes and Risk Factors

Anterior shoulder dislocations are responsible for most axillary nerve injuries. They account for 95% or more of all shoulder dislocations, and the force of the event can stretch or compress the nerve significantly. Fractures at the surgical neck of the humerus carry a similar risk, since the nerve wraps directly around that part of the bone.

Traction injuries are another common cause. Falls, vehicle collisions and motorcycle accidents can pull the neck and shoulder apart in ways that damage the nerve. Compression in the quadrilateral space, a small opening at the back of the shoulder, is a less common but recognized trigger. In rarer cases, shoulder surgery plays a role, accounting for roughly 6% to 10% of brachial plexus injuries during those procedures. Additionally, the nerve can be injured during surgical exposure or fracture open reduction and internal fixation, requiring interoperative management and repair or delayed repair for complex cases.

Patients over 40 also face a higher rate of axillary nerve damage after shoulder dislocation compared to younger patients.

Diagnosis

Diagnosing an axillary nerve injury starts with a detailed physical exam. Your physician will test shoulder strength, range of motion and sensation, and will check nearby nerves to rule out related problems like cervical radiculopathy or brachial plexopathy, since those can look similar.

Imaging is typically part of the workup. X-rays confirm whether a fracture or dislocation is present, while an MRI can pick up soft tissue changes and early signs of muscle atrophy. For the nerve itself, a nerve conduction study combined with EMG is the gold standard.

These tests confirm the injury, locate where along the nerve it occurred and create a baseline for measuring recovery over time. A first study is usually performed about three to four weeks after injury.

Treatment

Non-Surgical Treatment

Many patients with an axillary nerve injury do well with conservative care, especially when the injury came from traction or a reduced shoulder dislocation. Rest and activity changes protect the nerve early on.

A structured physical therapy program then takes over, focused on keeping the shoulder mobile, preventing stiffness and rebuilding strength as healing progresses. Follow-up exams and repeat electrodiagnostic testing track whether the nerve is responding as expected.

Surgical Treatment

When damage is severe, when there is penetrating trauma or when a patient has shown no real improvement after three to six months of conservative care, surgery becomes the right conversation. Options may include:

• Nerve grafting
• Neurolysis
• Nerve transfer
• Tendon and muscle transfer for cases where significant atrophy has already occurred

Recovery

Nerve tissue grows back at roughly 1 millimeter per day. That is slow, and it means that real improvement is measured in months, not weeks. Milder injuries, where the nerve is bruised rather than torn, often recover on their own within a few months. More significant nerve damage can take six to nine months or longer. Injuries that show no progress by that point may need surgical evaluation.

Physical therapy and rehabilitation matter throughout the entire process. Guided exercise protects the shoulder from stiffness and muscle loss while the nerve does its work.

Get Evaluated by New Jersey’s Hand & Upper Extremity Specialists

Shoulder weakness and numbness after a fall or dislocation deserve prompt attention. An axillary nerve injury can be easy to overlook early on, but catching it quickly expands your treatment options and improves how recovery goes.

The hand and upper extremity surgeons and specialists at University Orthopaedic Associates are experienced in diagnosing and treating nerve injuries of the shoulder and upper arm. UOA has six locations across New Jersey, in Somerset, Princeton, Wall, Woodbridge, Morganville and Monroe, so expert care is close to where you live. Request an appointment today.