Shoulder dislocation: what is it?

By Cristiano Antonino On May 31, 2023

Let’s talk about shoulder dislocation: the skeleton of the human body is made up of bones, all linked and connected to each other thanks to the joints which, based on their degree of mobility, are classified into fixed joints, mobile joints and semi-mobile joints

The movable joints – such as that of the shoulder – in order to have the mobility they are equipped with, are surrounded by a system of ligaments, the joint capsule, tendons and muscles for support.

Following a generally traumatic event, the system that keeps the two joints connected to each other gives way: this slippage is called dislocation.

The medical term “luxation” – from the Latin “luxus” = “gone out of place”, “dislocated” – in fact indicates a condition that occurs when, within a joint, the joint heads lose their physiological position without experience a fracture in the affected bones.

Dislocation, as regards the shoulder in particular

Its articulation is in turn formed by five different joints, the main of which is the scapulomeral or glenomeral joint, which connects the head of the humerus with the glenoid cavity of the scapula.

Such a large number of joints allows the shoulder to be by far the most mobile joint in the human body, capable of performing large and extremely complex movements.

Precisely because of its extreme mobility – certainly supported by an intricate system of muscles and tendons – that of the shoulder is among the joints most subject to dislocation phenomena.

Shoulder: two types of dislocation

Since a dislocation of the shoulder joint occurs, two types can be distinguished: anterior shoulder dislocation and posterior shoulder dislocation.

Anterior shoulder dislocation

In the event of anterior shoulder dislocation, the head of the humerus comes out of its physiological location – the glenoid cavity of the shoulder – sliding forward and downwards from its usual position.

This is by far the most common dislocation involving the shoulder, an estimated 95% of cases.

Posterior shoulder dislocation

In the case of posterior dislocation of the shoulder, the head of the humerus protrudes from the glenoid cavity of the shoulder, moving backwards from its physiological position.

This type of dislocation is very uncommon and much more complicated to treat.

In both anterior and posterior shoulder dislocations, the event can lead to the rupture of numerous anatomical structures, including bones, skin, ligaments, articular cartilage, capsule and muscles.

In particular, in the case of anterior dislocation of the shoulder, the rupture of the glenoid labrum, a sort of cushion that allows the humerus to slide easily inside the glenoid cavity, is very common.

After the rupture, the glenoid labrum tends to position itself and heal autonomously, but it is said that the positioning and healing will bring it back to its original functionality.

If this takes on a “spoiled” appearance, it is possible that the humerus is no longer able to slide as it did before the trauma, leading to an alteration and a decrease in joint function.

This specific, rather frequent medical condition is known as a Bankart lesion and often requires – to be corrected – surgery to restore correct joint function.

If, on the other hand, the dislocation is accompanied by a fracture of the humeral head, we are in the presence of a Hill Sachs lesion, much more frequent in elderly patients than in young ones due to the greater fragility of the bone tissue.

Shoulder dislocation: symptoms

The presence of a shoulder dislocation is easily identifiable by its characteristic symptoms: impossibility of movement of the joint, immobile arm that remains dangling adherent to the body, rather violent pain, swelling, bruised skin, evidently deformed shoulder and deprived of its characteristic roundness .

The causes of a dislocated shoulder

Dislocations can generally be divided – based on the cause that triggered them – into traumatic dislocations, congenital dislocations and pathological dislocations.

Shoulder dislocation is frequently caused by traumatic events, often occurring during sports performances.

Precisely for this reason, to accuse the phenomenon of shoulder dislocation more frequently are male subjects compared to female subjects, and young patients compared to elderly patients.

This is because young male subjects are more involved in contact sports, even violent ones.

Among these we remember basketball, rugby, baseball, skiing, competitive wrestling, in which it is easy to suffer a strong traumatic event that causes the humerus to dislocate from its physiological location.

Among the injurious mechanisms affecting the shoulder, the following are those most frequently encountered:

Fall with support on the rotated arm extended outwards, placed in that position to try to protect the rest of the body from falling.
Trauma to the internally rotated and adducted arm causing a posterior dislocation.
Shoulder fall.
Abrupt and violent movement of the arm carried above the head.
Abrupt and violent jerking of the arm backwards and outwards, perhaps by an opponent.
Violent collision between the shoulder and a hard surface: against a wall or an opponent.
Cartilaginous instability of the shoulder, congenital or acquired.
Chronic insanity of the shoulder joint due to excessive training which involves overloading of the muscles capable of supporting the joint.

The diagnosis of a shoulder dislocation

That of a shoulder dislocation is – for any doctor, but especially for the orthopedic specialist – quite simple.

The ease of the aforementioned diagnosis is due to the fact that the damage caused by the dislocation of the scapulohumeral or glenohumeral joint is quite evident both to the naked eye and to a simple palpation.

The shoulder will have lost its normal round shape and will appear bumpy

To verify this initial diagnosis, it will still be advisable to perform a series of diagnostic tests in order to have the most complete overview possible of the clinical picture of the patient presenting shoulder dislocation.

X-rays and magnetic resonance imaging may therefore be required in order to highlight the possible presence of further complications (bone fractures, nerve injuries, blood vessels, etc.).

Shoulder dislocation: proper treatment and rehabilitation

Just as happens for any other joint dislocation, also and especially for the dislocation involving the shoulder it is necessary to intervene promptly – always within 24/48 hours of the traumatic event – to implement the reduction (repositioning) intervention of the articulation.

The reduction surgery must necessarily be performed by a specialized doctor, who is generally an orthopedic surgeon, who will perform it under anesthesia to limit the pain during the relocation.

Once the reduction of the dislocation has taken place, the orthopedic surgeon immediately requests an X-ray, in order to verify if the operation was successful and the humeral head was correctly repositioned inside the glenoid cavity.

Finally, the arm could be immobilized for a period of one or two weeks so as to allow the correct healing of the joint; or it could be subjected to early mobilization, in combination with a muscle strengthening program.

This second option is generally chosen in cases of recurrent and recurring dislocation, especially in sports patients under the age of 30.