Causes of Shoulder Pain and Weakness

Causes of shoulder pain and weakness can vary in both younger and older people. You might experience minor "clicks" and aches or have persistent, debilitating pain and severe restriction of motion.

While injury and arthritis are among the more common causes of shoulder weakness and pain, there are other conditions that can give rise to these symptoms. They include shoulder impingement, rotator cuff tears, and shoulder inflammation.

Shoulder Impingement

Shoulder impingement syndrome (also known as swimmer’s shoulder or thrower’s shoulder) is caused by irritation and inflammation of the rotator cuff's tendons or bursa as they pass through a space just below the scapula, called the subacromial space.

Impingement is often caused by the repeated, overhead motion of the arm. It can result in pain when you lift your arm to the side, a condition referred to as the painful arc.

If left untreated, an impingement can lead to the gradual tearing of tendons around the rotator cuff as they begin to weaken and thin.

Rotator Cuff Injury

The rotator cuff is a group of four muscles and tendons that surround the ball of the shoulder joint. These structures together help lift the arm and perform overhead tasks.

A rotator cuff tear can be the result of sudden injury or microabrasions caused by ongoing inflammation. In some people, there may be few, if any, symptoms (particularly older adults who are inactive).

In others, symptoms can be more pronounced and include:

• General weakness in the shoulder
• Pain when you move, especially when you reach overhead or behind your back
• Limited range of motion
• A popping or clicking sound in your shoulder
• Pain at night
• Possible bruising on your shoulder

Rotator cuff tears can cause shoulder weakness by altering the mechanics of the joint. If left untreated, a person's range of motion and strength can be permanently affected.

Shoulder Inflammation

Untreated shoulder impingement or injury can result in an inflammation of the bursa (bursitis) or the tendon (tendonitis). It can also be caused by a condition called brachial neuritis, which is inflammation of certain nerves.

Over time, the lack of movement can lead to increased weakness and a loss of muscle mass, strength, and endurance.

While many of the symptoms of these conditions are similar, they have differences, as well.

Bursitis

Bursitis is the inflammation of the fluid-filled sacs (bursa) that help reduce friction in your shoulder space.

The appearance of symptoms tends to be gradual rather than immediate. The pain is localized around the outside of the shoulder. There may also be swelling, tenderness, and excessive warmth at the site.

There is generally little pain if you hold your arm to your side or lift it to a 90-degree angle.

Tendonitis

Tendonitis, by contrast, affects the tendons of the rotator cuff, causing pain in both the shoulder and upper arm (sometimes extending as far as the wrist).

Shoulder clicking is common, often more so when you reach behind your head or back. Pain can be felt when raising your arm above your shoulder or sleeping on the shoulder itself. As tendonitis progresses, the pain can become more persistent and severe.

Persons with shoulder tendonitis may also experience weakness, swelling, tenderness, and loss of range of motion.

Brachial Neuritis

Brachial neuritis can cause inflammation in a group of nerves that service the shoulder and arm, which is called the brachial plexus.

Also known as Parsonage-Turner syndrome, the condition is characterized by the sudden onset of a piercing and sharp pain. The severe pain tends to last for several days, after which the arm and shoulder are usually very weak. Other symptoms may include numbness or abnormal sensations (such as tingling or burning) in the shoulder or arm.