A Comprehensive Guide to Shoulder Dislocation in 2023

Everything You Need to Know About Anterior, Posterior, and Inferior Shoulder Dislocation

The shoulder is the most likely joint in your body to dislocate, often coming out of place during contact sports such as football, rugby, and martial arts. The ball and socket mechanism of the shoulder joint makes it very mobile, which allows your arm to get into all sorts of positions, but also means it’s more vulnerable to dislocation. There are a few different types of shoulder dislocation and the treatment and complications for each type can differ.

Shoulder dislocation usually happens because of a blow to the shoulder or fall on an outstretched arm – occurring during sports injuries, falls, and trauma. Complications of shoulder dislocation can include:

• Fracture of your clavicle (collarbone) or humerus
• Muscle, ligament, and tendon sprains and tears
• Damage to the nerves that pass nearby your shoulder joint, causing numbness and weakness
• Chronic shoulder instability – which makes you prone to having further injuries and dislocations

When your shoulder dislocates, it can move forward, backward, or downward. In this guide, we will discuss these types of shoulder dislocation and the difference between a full and partial shoulder dislocation.

You can also check out our guide to the best exercises for shoulder dislocation.

Anterior Shoulder Dislocation

Anterior shoulder dislocation, where the top of your humerus (the “ball”) moves forwards and away from the glenoid cavity (the “socket”), is by far the most common type of shoulder dislocation – making up around 97% of shoulder dislocations.

The groups most commonly affected by anterior shoulder dislocation are young men – generally from sports injuries and trauma – and older adults, often from falls. The mechanism of anterior shoulder dislocation is usually due to a high force of external rotation occurring while the arm is out.

Let’s make that easier to understand. Hold out your arm horizontally with the elbow bent at 90 degrees so that your hand is pointing at the sky with your palm facing forward.

While keeping your upper arm horizontal and your elbow at 90 degrees, rotate your forearm so that it’s pointing at the ground.

Pretty easy, right?

Now get into the original position and try to rotate your forearm in the opposite direction. If you’re keeping everything else still, you should feel discomfort in the front of your shoulder.

In anterior shoulder dislocation, a force is applying additional pressure in this position, but your arm can’t move any further back, and so the “ball” part of your shoulder joint dislocates forwards out of the joint.

Signs of an anterior shoulder dislocation include:

• Pain in the shoulder with difficulty moving your arm
• A “bump” in your shoulder, meaning it loses the normally rounded appearance
• You may be able to feel the top of your humerus on the front of your arm, slightly below the shoulder joint
• When the most comfortable position for your arm is to hold it slightly out from your body
• Numbness in your arm (a sign of potential nerve damage)

You may have seen some people – those who suffer from shoulder instability and have frequent anterior shoulder dislocations – put the joint back in place themselves. This can be dangerous, especially if this is your first dislocation. Shoulder dislocations are frequently associated with fractures, nerve injuries, and rotator cuff tears. If you try to treat it yourself, you may cause further damage or miss a treatable condition.

Before being treated, an anterior shoulder dislocation requires careful examination by a healthcare professional, followed by an x-ray to check for fractures. If there are no complications, the shoulder joint can be treated using a shoulder relocation technique.

Sometimes anterior shoulder dislocation requires surgery – either when the shoulder cannot be relocated with simple techniques, or when there is associated damage to the nerves, tendons, and muscles of the shoulder. Minimally invasive shoulder surgery, such as shoulder arthroscopy, is the treatment of choice where simple measures have failed.

Recurrent dislocation of the shoulder can be a problem for anyone who suffers from an anterior shoulder dislocation, particularly if their first dislocation occurred at a young age. Those who suffered from a shoulder dislocation under the age of 25 are very likely to suffer from a further dislocation at some point in their lives.

Anterior Shoulder Dislocation X-Ray

An x-ray is the main, and often only, investigation required to diagnose an anterior shoulder dislocation. This is usually performed in the emergency room, giving your emergency medicine physician or orthopedic surgeon the ability to quickly diagnose and treat the problem without the need for more intensive tests like an MRI scan.

There are two main views that are used to diagnose shoulder dislocation: the AP (anteroposterior) view and the Y view. The AP view shows the front of the shoulder, while the Y view shows the top of the shoulder.

In a normal shoulder, the humeral head (the ball-shaped bone at the top of the arm) fits snugly into the glenoid fossa (the socket in the shoulder blade). In a shoulder dislocation, the humeral head has moved out of this socket.

On an x-ray, a shoulder dislocation will appear as a gap between the humeral head and the glenoid fossa. There may also be other signs of injury, such as fractures of the humeral head or the clavicle.

Below you can see Anterior-posterior views (AP) of two shoulder X-rays, comparing a normal shoulder X-ray with an anterior dislocation. Here you can clearly see how the head of the humerus (the “ball”) has moved anteriorly (forwards) and no longer sits nicely against the glenoid fossa (the “socket”).

In most cases, an X-ray is the only investigation required to diagnose shoulder dislocation. However, in some cases, additional imaging tests, such as CT or MRI, may be needed to get a more detailed view of the injury.

Posterior Shoulder Dislocation

Posterior shoulder dislocations, where the shoulder dislocates and moves backwards, is the second most common type of shoulder dislocation – occurring in about 2-4% of all cases.

Young adult men are the group most affected by posterior shoulder dislocation. These usually occur due to trauma, such as in sports injuries or car accidents, or seizures, where uncontrolled and violent movements of the muscles cause the shoulder to dislocate in this uncommon manner.

As posterior shoulder dislocation is less common than anterior shoulder dislocation, there is a risk that it can be misdiagnosed. If the symptoms of shoulder dislocation are present but the initial (anteroposterior) x-ray is normal, additional x-rays should be performed to check for posterior dislocation.

Signs of a posterior shoulder dislocation include:

• Pain and loss of movement in the shoulder
• An abnormal-looking shoulder – with bumps and dips instead of a smooth round appearance
• When the most comfortable position for your arm is to hold it in front of your torso with your elbow bent – like someone who has their arm in a sling

Almost a third of patients with posterior shoulder dislocation have an associated fracture, and complications are more likely the longer it takes to get treatment. As there is an association with fractures, an x-ray or CT scan must be taken before there is an attempt to relocate the shoulder joint.

Treatment for posterior shoulder dislocation may require more sedation and pain relief than anterior shoulder dislocation and may sometimes require shoulder surgery – particularly if there is an associated fracture.

Posterior Shoulder Dislocation Xray and MRI

While an anterior shoulder dislocation is usually visible on an anteroposterior xray, posterior shoulder dislocations may be missed on anteroposterior x rays 50% of the time. If there are signs of a dislocation, but the frontal radiograph is normal, an axillary view xray should be taken, or an MRI scan if this is available.

AP View

Lateral View

These x rays show a full posterior shoulder dislocation – both anteroposterior and lateral views have been obtained to confirm diagnosis. The humeral head (top of the bone in the upper arm) is fixed in internal rotation, meaning it has a rounded appearance – known as the lightbulb sign – commonly seen on posterior shoulder dislocation xray.

This MRI scan shows a “reverse Hills-Sachs defect” – an injury often associated with posterior shoulder dislocation. MRI and CT scans can be used to help identify posterior shoulder dislocation and rule out associated fractures.

Inferior Shoulder Dislocation

Inferior shoulder dislocations are the rarest form of shoulder dislocation, accounting for roughly 0.5% of cases. The name means that the humeral head (the “ball” of the shoulder joint) dislocates downwards out of the glenoid cavity (the “socket”). This form of dislocation is often referred to as luxatio erecta, the name coming from the typical presentation where the patient’s arm is held above their head.

Trauma is the most common cause of inferior shoulder dislocation, such as when someone is holding their arm above their head to grasp something as they fall. An example of this is when a motorbike rider falls off their bike, with their arms reaching above their head so that when their arm hits the ground the arm faces extreme pressure and dislocates inferiorly (moves downwards). 

An inferior shoulder dislocation is typically very painful and is often associated with fractures and nerve injuries, causing numbness and weakness in the arm. When evaluated in a hospital, these injuries require careful clinical assessment and imaging to examine the extent of the injury. Shoulder surgery will be required if there is significant damage to the joint, or if the treating clinician cannot relocate the joint.

Even if your treating clinician can relocate the shoulder joint without surgery, you are likely to have limited shoulder movement for 2-6 weeks. Many of those affected by inferior shoulder dislocation will, unfortunately, suffer from recurrent shoulder dislocation.

Partial Shoulder Dislocation

Partial shoulder dislocation, also known as shoulder subluxation, is when the head of the humerus (the “ball” of the shoulder joint) partially comes out of the glenoid cavity (the “socket”) but does not completely come out of place.

Shoulder subluxation has similar symptoms to a full shoulder dislocation, but the shoulder deformity might not be as clear. Symptoms include:

• Shoulder pain
• Difficulty moving your shoulder
• Swelling and deformity in the shoulder joint
• Numbness in your arm

While with full dislocations you are often unable to move your arm at all, with partial shoulder dislocation you may be able to move your arm, albeit with some discomfort and sometimes a catching sensation – particularly for overhead movements.

Partial shoulder dislocations are caused by sports injuries, trauma, and falls. In partial dislocation, the blow to the shoulder was generally not sufficient to fully dislocate the joint.

You’re more likely to experience shoulder subluxation if you’ve previously suffered from a shoulder dislocation, or have been diagnosed with shoulder instability. This is because the ligaments, muscles, and cartilage of the shoulder joint is damaged and looser, making the movement of the humeral head out of the socket easier. 

For this reason, it is important that you seek appropriate treatment to strengthen your shoulder joint after a partial or full dislocation.

Shoulder Dislocation Treatment

Treatment for shoulder dislocation depends on the severity of the injury, whether you’ve suffered any of the complications, and what type of dislocation has occurred. Many shoulder dislocations can be treated in the emergency department following careful assessment, using sedation and pain relief.

Here is an example of how a clinician relocates a dislocated shoulder (this should never be attempted by those without proper training):

If you’ve suffered a shoulder dislocation which has been relocated without surgery, you will have a few weeks of limited shoulder movement and rehabilitation before you can fully move your arm again. It may also be difficult to sleep.

Your doctor may place your arm in a sling for a short time following a shoulder dislocation. Other rehabilitation activities your doctor may recommend include:

• Resting your affected arm for several weeks
• Avoiding any heavy lifting or awkward overhead movements
• Simple pain relief such as acetaminophen or ibuprofen
• Ice packs placed on your shoulder several times a day for the first few days
• Once the inflammation has improved, switching to heat packs
• Light exercises as directed by your orthopedist or physical therapist

Sometimes shoulder dislocation requires surgery to repair damaged tissue and treat complex dislocations. You must always seek professional help following a shoulder dislocation – if you try to treat it yourself you may end up with nerve damage or an untreated fracture.

Conclusion

So that’s everything you need to know about shoulder dislocation! We’ve covered all of the different types of shoulder dislocation, as well as how to get your shoulder back to usual after you’ve suffered a dislocation.

If you suspect that you have dislocated your shoulder, please avoid treating it yourself. Instead of risking a lifelong injury, book a consultation with an orthopedic doctor near you and get your recovery off to a good start.