Dislocated Shoulder Causes And Symptoms

Overview

Shoulder dislocation happens when the humerus - the large bone in the upper arm - moves out from its socket. The American Society of Orthopaedic Surgeons describes the shoulder joint as extremely flexible, and its ability to move in various directions contributes to it being the most commonly dislocated joint in the body. 

Types of dislocated shoulder

The position of the humerus in relation to the shoulder joint determines the dislocation type. 

There are three types - anterior (forward), posterior (backward) and inferior (downward). Of these subtypes, anterior dislocations are the commonest and are thought to account for 97% of all shoulder dislocations.¹

Dislocations can also be partial or complete. A partial shoulder dislocation occurs when only part of the humerus comes out from the socket and a complete dislocation is when the entire humerus leaves the socket. 

All types of shoulder dislocations can cause significant pain. They can also cause damage to the structures in the upper arm such as surrounding soft tissues (e.g. arteries, veins, ligaments, and nerves), so medical attention should be sought right away if you suspect you have dislocated your shoulder.

Causes of a dislocated shoulder

The cause of a shoulder dislocation typically determines the type of dislocation seen. 

• Anterior dislocation occurs when a person falls onto an outstretched arm or when the arm is in a throwing position¹ 
• Posterior dislocation occurs due to abnormal muscular contractions e.g. during a tonic-clonic seizure, due to an electrical shock, when grabbing the dashboard during a motor vehicle accident or when falling onto an outstretched hand²
• Inferior dislocation is the least common type. It can occur when there is a high-energy injury such as a motor vehicle collision which causes the humerus to be pushed against a part of the shoulder blade called the acromion. This happens when the arm is outstretched above the level of the head³

Signs and symptoms of a dislocated shoulder

When a shoulder becomes dislocated, there is usually a history of injury. Symptoms may include:¹ 

• Pain when moving the arm
• Weakness of the arm
• A popping sensation 
• Deformed appearance of the shoulder
• Numbness
• Swelling and/or bruising 

Management and treatment for a dislocated shoulder

The management of a shoulder dislocation depends on the physical assessment. After this, an X-ray is usually performed to assess the location of the bones and to exclude any fractures. 

If it is considered suitable by the medical team, the shoulder joint will be reduced by a trained professional. Reduction involves manually moving the bones back into their normal anatomical position. This can be performed in the emergency department with sedation or local anaesthesia to reduce the pain. 

After successful reduction, the X-ray should be repeated to confirm the humerus is back in place. An examination of the nerves should also be performed.¹

In cases where reduction is not suitable or multiple failed attempts have been made, an orthopaedic surgeon may be consulted to determine whether surgery would be beneficial. The surgical options include arthroscopic or open surgery.⁴

Recovery from a shoulder dislocation takes between 12-16 weeks. It is essential to wear a sling in the initial few weeks. 

Your healthcare team should then organise a follow-up appointment with the orthopaedic team. It is also important to rebuild the strength of the upper arm and shoulder muscles through shoulder rehabilitation exercises, guided by a physical therapist, to help reduce the risk of another dislocation. 

Diagnosis

You should seek medical attention if you are worried about an injury and possible dislocation of the shoulder. 

A medical professional in the emergency department will take a detailed history of the events leading up to the injury and your symptoms. They will also examine the joint for any abnormalities. In some cases, such as anterior dislocations, it may be possible to diagnose you just by feeling for the location of the humerus head (the top of the upper arm bone which sits in the shoulder socket) in the joint.

They will also check for any numbness or loss of sensation and loss of strength in the arm, which may indicate damage or compression of the nerves caused by the dislocated position of the humerus bone. One of the nerves that can be affected is the axillary nerve. This is because of its location close to the humerus. If it is affected by the dislocation, sensation may be reduced around the outer part of the shoulder. Once the joint is reduced, the sensation usually returns to normal.¹

It is important that the medical team also investigate any possible fractures in the bones of the shoulder joint before attempting to put the humerus back into the shoulder socket. 

Once a complete assessment has been made, the medical practitioner can recommend the best treatment course.

Risk factors

Shoulder dislocations can occur at any age. Any activity that involves extreme arm rotation can result in shoulder dislocation. Those more at risk include athletes playing contact sports and motorists involved in collisions.¹

Complications

If surgery is not performed initially, the shoulder may become dislocated again in the future due to the damage and instability caused by the initial injury. The risk of this occurring decreases with age at the time of the first dislocation.⁴ It is also more common when there has been damage to the rotator cuff muscles.¹ These muscles connect the shoulder blade and the humerus and can become damaged or torn during a dislocation. 

In people with repeated dislocations, there is also a greater risk of developing osteoarthritis in the shoulder joint due to recurrent damage to the bones. If surgery was not performed initially, it may be required further down the line to stabilise the shoulder joint and prevent future dislocations. 

FAQs

How can I prevent a dislocated shoulder?

You can reduce your risk of suffering a shoulder dislocation by strengthening the muscles around the joint. You can also reduce your risk by avoiding contact sports or wearing proper protective gear whilst participating. 

How common is a dislocated shoulder?

Shoulder dislocations represent roughly 50% of all joint dislocations. It is the most common type of dislocation in the body. 

Can a dislocated shoulder fix itself?

A shoulder dislocation requires reduction. This should only be performed by a trained medical professional. If left untreated, it can lead to severe pain and may make it more difficult to reduce in the future.

When should I see a doctor?

If you suspect you have a dislocated shoulder, you should seek medical attention for proper assessment and management. You should not try to push it back into place by yourself as this can cause further damage to surrounding structures. 

Summary

Shoulder dislocations can occur to anyone at any age. They can cause significant pain and loss of normal shoulder movement. It is important to seek medical advice if a dislocation is suspected so that they can diagnose and treat it appropriately. After a shoulder dislocation is treated, it is beneficial to work with a physical therapist and the orthopaedic team to improve the strength and flexibility of the joint to help to prevent future dislocations from occurring.