What Causes Shoulder Pain?

Shoulder pain is common, and it’s tricky to treat. Often, shoulder problems persist for many months before improving. Sometimes this pain will continue.

Pain can focus on several different sites around the shoulder complex. Familiar places for it to occur include the upper outer arm, where the deltoid muscle is, and across the top of the shoulder, where the upper trapezius muscle is. Pain is also commonly felt between the shoulders, at the back of the shoulder, or running down the front of the upper arm, where the biceps tendon is. What often makes shoulder pain hard to diagnose is that it feels nonspecific and vague around the shoulder, and it is not usually point-specific or easy to target. Nerves are an uncommon but often overlooked cause of shoulder problems and pain. It's frequently assumed that nerve pain must include burning, pins and needles, or numbness. Although this is often the case, it is not 100% accurate, and sometimes a patient experiences only one symptom, pain, that indicates a problem with a nerve. We gave an overview of nerve anatomy in our previous blog, titled ‘Basic Anatomy: Nerves’ (might be good to add a link here).

What Are the Essential Nerves Around the Shoulder?

There are several vital nerves around the shoulder. Here we will go through them, some of the symptoms, and common pathologies related to them and why you might experience shoulder pain as part of the problem:

1) Axillary Nerve: The axillary nerve branches off the posterior cord of the brachial plexus. This is the network of nerves that originates in the spinal cord, extends to the neck, and ultimately supplies all the nerves to the arms. This particular nerve supplies sensation to a patch of skin just at the top of the upper arm. It's often referred to as the Regimental Badge area, where an army officer's regimental badge would sit on his uniform, and it helps people know where we mean. This area of symptoms is often misdiagnosed as rotator cuff problems or referred neck pain. Treatment is not targeted accurately.

The axillary nerve can be injured when a person dislocates their shoulder. This is because the nerve is stretched when the dislocation occurs as it passes across the front of the shoulder joint. This injury will already be excruciating on its own due to the other injuries and issues, and if it persists, it can cause problems with this nerve. Particularly if numbness or pain occurs over this regimental badge area, and if the muscle this nerve supplies remains weak. This is the deltoid muscle, which lifts the arm out to the side and front. This nerve must be thoroughly evaluated if you have persistent regimental badge pain or numbness.

2) Long Thoracic Nerve: Another of the brachial plexus nerves, the long thoracic nerve follows a winding path down the back of the shoulder to the serratus anterior muscle that it supplies. This nerve does not often cause many problems with sensation along its course, and more often, what is seen is persistent weakness in the lower inner border of the shoulder blade, seen as a ‘winging’ shoulder blade. If pain is felt, it is a burning pain under the shoulder blade or in the mid back that cannot be easily alleviated. This area of symptoms is often diagnosed as thoracic spine problems or postural problems, and so treatment is not targeted accurately. Testing of the serratus anterior muscle is essential to identify weakness or problems, and a clear history-taking is needed to analyze whether force has been applied to this nerve, for example, by pulling force through the arm or a hit to the back ribs with the arm outstretched. This diagnosis can then be made, and the appropriate treatment delivered.

3) Suprascapular Nerve: The suprascapular nerve supplies the main shoulder joint and also the acromioclavicular joint (the joint between the collar bone and the shoulder). This means that pain that occurs over the top of the shoulder and at the point of the shoulder could be due to a problem with the suprascapular nerve. This area of symptoms is often diagnosed as a rotator cuff problem or osteoarthritis of the acromioclavicular or shoulder joint. So treatment is not targeted accurately, as nerve problems need a different course of action. This nerve supplies two of the rotator cuff muscles that form an essential network around the main shoulder joint: supraspinatus and infraspinatus. These muscles provide rotation movements to the shoulder joint. Often, this difficulty with rotational movements is seen but misdiagnosed as a problem with the muscle itself rather than the nerve that supplies it. It is always essential to fully evaluate both the nerve to the muscle and the muscle.

These three nerves can all cause shoulder pain and problems. Assessing them to ensure the correct diagnosis is reached is vital, as many are often overlooked in favor of more common, easier-to-diagnose problems. If your shoulder pain has been persistent or is not responding to your current plan, consider evaluating the nerves.

Should you be concerned about how you’re moving and walking, contact us now to help and get you going again – call.

Written by

Leanne Plenge

Chartered Physiotherapist