All about shoulder instability
Shoulder instability is the propensity to dislocate due to errors in the structure of the shoulder girdle. In this article, consultant orthopaedic surgeon Mr Panetlis Tsantanis explains why shoulder instability occurs and what can be done to correct it.
What is the shoulder?
The shoulder joint is comprised of the top of the upper arm bone (the humerus), the collarbone (clavicle), and the shoulder blade (scapula). These bones are anchored together by a network of muscles, ligaments, tendons, and cartilage. and a sac of fluid called a capsule which provides lubrication for the bones to move. The configuration of the joint is a ball-in-socket – the humeral head fits into a niche of the scapula – and this enables a wide range of arm movement like abduction, flexion, and extension.
What is shoulder instability?
Instability of the shoulder joint means that the joint is not sufficiently held together because the ligaments, capsule, or labrum – which is the cartilage between the bones – has been torn, loosened, or stretched. This can be due to dislocation/subluxation, a labrum tear, or a genetic condition.
Dislocation
The humeral head is prone to ‘pop’ out of its normal position in the niche, either partially in what is called subluxation, or completely in what is called dislocation. This may happen after an initial traumatic incident – such as a car accident, sports injury, or a fall. Even though the bones may be reset after this incident, these structures can remain damaged, which allows the opportunity for future dislocation or partial (subluxation) dislocation.
Labral tear
The labrum cartilage keeps the humeral head in place within the scapular niche while also providing shock absorption. The labrum can be torn due to a traumatic injury, but it can also happen due to overuse, which can happen to athletes and people who use their arms a lot at work.
Genetic condition
Some genetic conditions can cause the ligaments to naturally be looser and thus more vulnerable to stretching and dislodgement, like Ehlers-Danlos.
What are the symptoms of shoulder instability?
The symptoms of shoulder instability include:
- Weakness or difficulty when trying to lift the arm
- Pain when trying to move the shoulder
- A ‘frozen’ shoulder
- Hearing or feeling a pop in the shoulder
- Swelling or bruising
- A feeling of ‘looseness’
- Reduced range of motion
How is shoulder instability treated?
Shoulder instability is usually diagnosed after a physical exam and an imaging scan, like an X-ray, to view the tissue structures and determine the extent of the instability.
After an initial shoulder injury, ideally, the arm should be rested and perhaps worn in a sling or brace to protect it and allow it to heal. Most people who have a shoulder dislocation or subluxation are not likely to have recurring instability, but others who are more likely to have their shoulder injured -- especially athletes – or a tear will be more at risk of having lasting instability, necessitating more intensive treatment. This could include nonsurgical approaches, such as:
- Physical therapy, to strengthen the muscles supporting the joint to reduce pain and increase mobility
- Non-steroidal anti-inflammatory drugs to reduce swelling and pain.
Surgical treatments can vary depending on the cause of instability in the shoulder. Most procedures will aim to re-anchor loose or torn tissues and can be done with minimally invasive techniques, such as an arthroscopy. However, if the shoulder is very damaged, an open procedure may be more effective.