Shoulder Instability: Causes, Symptoms, Diagnosis, Risks, and Treatment

The shoulder is a ball and socket joint allowing a wide range of movements of the arms. The top part of the upper arm bone (humerus) sits in the hollow cavity of the shoulder joint and is held by ligaments and cartilage. Sometimes, the range of motion may get restricted due to shoulder instability, which can occur due to many reasons and may lead to recurrent instability. Surgical and non-surgical treatment methods may help to treat and manage shoulder instability.

What is shoulder instability?

Shoulder instability is a term used to describe a condition in which the humeral head pops out of the shoulder socket cavity, causing discomfort and loss of movement function. This can be a dislocation that lasts for a few seconds or minutes, or it can also have a greater impact, and the dislocation requires assistance to be corrected. 

In the event of shoulder instability, there can be collateral damage to the shoulder. Labral tears (injury to the soft cartilage around the glenoid), rotator cuff tears, cartilage injury, and fractures may occur alongside shoulder instability. Shoulder instability may occur as a result of serious trauma like falling or colliding forcefully. But it may also occur without being involved in a traumatic incident, such as in the case of Ehlers-Danlos, which is a genetic disorder affecting the connective tissues in the body.

What are the symptoms of shoulder instability?

The most common symptom of shoulder instability is pain in the affected shoulder region. Some people may also feel heaviness in the affected shoulder as though the arm is coming out of the socket joint. This may feel more pronounced when the person makes specific arm movements. There can also be swelling or visible bruising in the affected area of the shoulder.

There is a range of other signs of shoulder instability which can be experienced by affected individuals. The shoulder instability symptoms may manifest in one or more of the following ways:

• Feeling or hearing popping of the shoulder joint
• Weakness of the arm, especially when lifting or making movements requiring muscular force
• Feeling like the arm/ shoulder is stuck
• Heightened sensation of movement in the ball and socket joint

Causes of shoulder instability

The most common cause of shoulder instability is physical trauma or injury, such as collision or falling. It is most prevalent in sports persons who need to make repeated arm or shoulder movements, such as in cricket or tennis. However, there can be some conditions or cases which may lead to shoulder instability. Such causes of shoulder instability may include the following:

• Sliding or diving 
• Seizure disorders 
• Genetic conditions such as Ehlers-Danlos
• Overuse of the shoulder causes muscle fatigue

How is shoulder instability diagnosed?

When a person experiences the symptoms of shoulder instability, a doctor performs a complete physical examination of the patient for diagnosis. The history of previous injuries may also be required for diagnosis. During the physical examination, the doctor may check for points of tenderness and check for the arm's range of movement. Looseness of the shoulder joint may also be determined and assessed during the physical test.

Imaging tests may be required to explore the possible causes of shoulder instability. An X-ray may provide the necessary information to diagnose or rule out the possibility of fractures. Additional tests may be required, such as a Magnetic Resonance Imaging (MRI) scan and/or a dye test (arthrogram), which may help to investigate the shoulder joints and tissues further.

How is shoulder instability treated?

Patients with complete or partial shoulder dislocation may find relief by providing rest to the affected arm and avoiding strenuous activities for a few days. In case the pain is significant, immobilisation using a cast and sling or shoulder bracing may be required. After the physical symptoms of pain and swelling subside, physical rehabilitation for restoring range of motion may be recommended. This series of treatments may be quite successful in patients and help them return to their daily life activities within a matter of a few weeks. The physical rehabilitation process is performed under the supervised guidance of physical therapy specialists.

Applying ice packs may help to reduce swelling. Taking nonsteroidal anti-inflammatory drugs (NSAIDs) may also help to alleviate pain and swelling. However, people with a higher risk of recurrence of shoulder instability or who have experienced shoulder damage previously may be recommended to undergo surgical treatment. 

Surgical treatment of shoulder instability may be aimed at improving shoulder stability and aiding patients to resume their daily life activities as soon as possible. An arthroscopic surgery is performed by using an arthroscope, which may help to stabilize mild looseness. However, in case of severe shoulder instability, invasive open surgery may be required. Open surgery would allow surgeons to access the joint capsule, ligaments, and labrum, which can then be repaired or reattached depending on which part is causing the instability. 

The arthroscopy helps to repair the structures that were identified as the cause of the shoulder instability during diagnosis. It involves using sutures to perform the surgery or by using metal or plastic anchors to reattach ligaments and hold them in place. 

Risks    

While a shoulder instability condition may occur as a result of accidental trauma, some people may be at a higher risk of experiencing shoulder instability than others. These risk factors may include the following:

• Being young
• Participating in rigorous contact sports such as football, hockey, basketball, etc.
• History of a previous shoulder injury
• Having loose ligaments, common in swimmers, and dancers, or due to a genetic disorder 
• Seizure disorder

Complications

People who have experienced shoulder instability are at a higher risk of recurrent shoulder dislocation and arthritis in the shoulders. The higher the degree of instability, the more damage to the surrounding structures in the shoulder, i.e., in the bones, cartilage, and rotator cuffs.

When would I need surgery?

Surgical treatment of shoulder instability may be considered for people who have a physically active lifestyle or are involved in sports which may lead to future instability of the shoulder due to rigorous straining of the arms and shoulders. Surgery may also be recommended for those who have loose ligaments in the shoulders naturally and experience instability while doing routine daily activities such as sleeping and dressing. 

Conclusion

Shoulder instability may occur due to a number of reasons, and its risk of occurrence may depend upon certain factors. Both surgical and non-surgical methods of treatment are available to fix shoulder instability. With physical rehabilitation support, the full range of movement can be restored in about 6 to 8 weeks with a gradual return to other activities. The chance of shoulder instability recurrence after surgery is quite low (about 3-5%), and patients may resume their routine activities within a short time.