Kellie K. Middleton, MD

Causes and Symptoms of Shoulder Instability

Feb 20, 2022
Causes and Symptoms of Shoulder Instability
But what exactly is shoulder instability? The shoulder, being one of the most mobile joints in the human body, has a  ball-and-socket joint that helps in movement...

But what exactly is shoulder instability? The shoulder, being one of the most mobile joints in the human body, has a  ball-and-socket joint that helps in movement. Its wide range of movement makes it open to instability conditions and injuries. 

The upper arm bone (the humerus) and the shallow cavity (the glenoid) make the shoulder’s structure. 

The humerus is close to the shoulder socket. It is held into the socket by a capsule, a lining in the joint thickening called ligaments, and a labrum. When you experience shoulder pain, various activities such as taking care of personal hygiene and running errands may become impossible. 

Sleeping might also become stressful. Such a case is called shoulder instability. Our guide highlights some of the symptoms and treatments for shoulder instability

Let’s get started!

What Is Shoulder Instability?

When the head of the upper arm forces out of the shoulder bone, it causes shoulder instability. The shoulder tends to be slightly out of place, so the bones are not stable. 

Note that this is different from a shoulder dislocation. Shoulder dislocation is when the shoulder ligaments are torn and cannot hold the joint in place. The shoulders rely on tendons, muscles, and ligaments to keep them stable.

Common Symptoms of Shoulder Instability

Loose shoulder ligaments can contribute to shoulder instability. You can feel the shoulder joint ball is out of the socket, which is commonly associated with pain, swelling, and weakness. 

Shoulder pain can either start suddenly or slowly. For instance when you throw a ball or lift your arm above the shoulder. Below are some of the common symptoms of shoulder instability.

  • Shoulder Pain
  •  A loose or hanging sensation in the shoulder joint
  •  Repeated instances of shoulder dislocation and shoulder fatigue.
  •  Decreased range of shoulder motion
  •  Swelling of the shoulder

Causes of Shoulder Instability 

The common cause of shoulder instability is repetitive activities that strain the shoulder, like lifting heavy loads or working your arms at shoulder level. 

Various sports like football or volleyball can also cause shoulder instability. Athletes also face this problem since they involve heavy use of the shoulder.

Other causes of shoulder instability can be:

  • Injury: Most active patients, especially those who have dislocated their shoulder at one point, may have chronic shoulder instability. Some injuries caused by work or sports also lead to shoulder instability.
  • Anatomy: Sometimes, one may naturally experience loose ligaments that lead to shoulder instability due to injury or a repetitive strain.
  • Overuse of the Shoulder: This may lead to muscle fatigue or weakness

Types of Shoulder Instability

Now that we know what shoulder instability is, let us look at three different types of shoulder instability.

Anterior Instability 

Anterior instability is caused by dislocation and it is the most common type of shoulder instability. Men aged 18-25 years are vulnerable to this injury. Also known as the “dead arm” syndrome, a patient with this kind of instability may lose sensation, feel numbness, and tingling on the shoulder.

Posterior Instability

Posterior instability is less common than anterior instability. It is caused by muscle contractions such as seizures or a severe electric shock. Some of the people who may have Posterior instability are athletes due to their strenuous activities.

Multi-directional Instability (MDI)

This type of instability is caused by chronic dislocation of the shoulder. The shoulder joints become loose within the socket making the shoulder constantly shift around. Most people who face MDI involve themselves in strenuous sports such as swimming, gymnastics, baseball, and tennis. 

Some of the symptoms of MDI include:

  • Feeling weak on your shoulder or arm
  •  Feeling as though the shoulder is not in its position
  • Pain while using the shoulder – often experienced when making  overhead exercises such as aerobics, or carrying heavy objects

 Shoulder Instability Diagnosis

The first and most important step you should take is to have a professional doctor examine and have several tests done on your shoulder for any looseness. 

Some of these tests include:

  • Magnetic Resonance Imaging (MRI): This machine uses strong magnetic fields and radio waves to create detailed images of the bone and tissues in your shoulder. 
  • X-Rays: This is an imaging procedure that shows detailed pictures of the bones and internal structures. The results will show if the shoulder bone is in the right place. 

Shoulder Instability Treatment 

Depending on how bad the shoulder injury is, it is wise to seek treatment immediately. Treatment options may include:

Physical therapy

When your shoulder dislocates, it is important to rest it and avoid strenuous exercises for some days. You can also apply ice to the injured area to avoid swelling or use a sling if the pain persists. 

The sling helps prevent too much movement of the shoulder as you heal from an injury. When the pain subsides, it is advisable to begin the exercise with the help of a physical therapist. 


Shoulder surgery can help bring back the structure of the damaged ligaments, tendons, and muscles. This treatment is given when physical therapy doesn’t work. 

Some shoulder surgery requires minimally invasive arthroscopic surgery. It helps patients recover faster. In addition, surgery makes the shoulder tighter than before.

Risk Factors for Shoulder Instability

Several factors can cause shoulder instability. These include – repetitive overhead exercise and previous dislocation, or genetics. Athletes are also prone to shoulder instability. Other risk factors can be staying on the phone for a long time, or having a desk that is too high.

Request an Appointment Today

At Kellie Middleton, we provide treatment services for shoulder injuries – which include shoulder instability. 

The main symptoms of shoulder instability are weakness and pain. It may affect your motions of the shoulder like throwing a ball. Therefore, if you have numbness, pain, loose joints, or sudden shoulder injury, it’s best to visit your orthopaedic surgeon for treatment. 

You can also book an appointment with us. We will examine your shoulder and provide the appropriate medical treatment.