The shoulder is a ball and socket joint, it is made up of 3 bones that move together as one; the scapula (socket of the shoulder blade) and the head of the arm bone (ball section) and the collar bone.

The joint is designed to give a large amount of movement. This also means that it has the potential to be too loose. There are various structures that help to keep the joint in position. The most important ones are:

• Ligaments, which hold the bones together
• Labrum (A rim of cartilage, which deepens the socket)
• Muscles, which keep the shoulder blade and ball in the correct position when moving or using the arm.
• Joint capsule (lining that covers the joint)

Shoulder instability is when the ball is not suitably controlled within the socket. It can develop in two different ways; Traumatic and Atraumatic.

• Traumatic caused by a sudden injury of dislocation (joint moving fully out of place), or subluxation (joint partially moving out of place).
• Atraumatic when shoulder instability can occur without an injury, in people who naturally have greater laxity (looseness) in their joint and surrounding tissues.  Additionally, in a very small minority of people shoulder instability can occur due to muscle imbalances i.e some muscles pulling too strongly or not coordinating well enough.

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Symptoms of shoulder instability

Patients commonly complain of pain, weakness and poor movement and may feel apprehensive about moving their arm in certain ways. They may feel that their shoulder is slipping, giving way, catching or coming out of joint, which can cause patients to feel less confident about using their arm for general tasks of daily living, at work and during sporting activities.

If the problem develops following a sudden injury, patients may report that their shoulder repeatedly dislocates (comes out of joint) and need to visit the hospital to have it relocated (put back in), whilst other patients may feel as if their shoulder is partly coming out and then moving back in again (subluxing).

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How common is shoulder instability?

The shoulder is a very mobile joint, and therefore dislocation (the joint coming out of place) is more common than in some other joints.

Traumatic shoulder instability accounts for approximately 96% of shoulder dislocations.

The first time of dislocation is an important factor:

• If you first dislocate your shoulder before you are 30, there is a 70% chance of recurrent instability (the shoulder dislocating again in the future).
• If you are over 40 years old when the first dislocation happens, there is less than a 10% chance of reoccurrence.

Atraumatic (without injury) The true prevalence is unknown but thought to be approximately 4% of shoulder instabilities. Predominately in the younger age of under 25 years.

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What causes shoulder instability

Shoulder instability develops in two different ways:

• Traumatic cause: Due to a specific injury or trauma.  This can damage other structures in the shoulder such as ligaments, tendons, labrum (the rim of cartilage) or the bone in the upper arm (humerus).  This can increase the chance of the shoulder coming back out again or inhibit how the shoulder works.
• Atraumatic cause: the shoulder problem may not be linked to any injury. The person is either born with, develops laxity of their shoulder joint tissues

Shoulder joint laxity can also develop as a result of repetitive minor injuries, such as overhead throwing sports, that cause the shoulder structures to stretch out over time. Patients in this category can lose normal muscle control, causing the shoulder to become unstable whilst doing simple daily tasks and sporting activities.

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What helps with shoulder instability

Following a first-time dislocation/injury, your arm may be put in a sling. Your doctor or physiotherapist will advise you on when to remove it to exercise.

Making changes to the activities you do does not mean that you have to stop moving or stop using your shoulder altogether. Try to avoid activities that involve lifting your arm over your head, or contact sports for the first three months after the dislocation.

Atraumatic shoulder instability is a complex problem to treat. The shoulder is naturally too mobile, and you can’t control or move it correctly.

Resting the shoulder does not help, keeping your shoulder moving and the muscles strong is beneficial. Learning to recognise the triggers and learning how best to prevent or deal with it is necessary.

In most cases, specialist Physiotherapy input and hard work from you, is the best treatment option to help shoulder instability, whether due to an injury or not.

Physiotherapy helps patients regain their shoulder mobility and targets specific strengthening for the muscles that surround the shoulder to increase the stability. It also helps to retrain the brain, to coordinate and control shoulder movement and restore more normal movement patterns.

Please speak to a healthcare professional for guidance on how to improve your shoulder stability.

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Timescales/ Prognosis

Recovery timescales vary depending on the cause of the problem, and whether or not this is your first dislocation.

First-time dislocations with no structural damage can improve within 3-6 months.

Patients will be advised to avoid heavy lifting and sports involving shoulder movements for between 6 weeks and 3 months.

You’ll probably be off work for 2 to 4 weeks, or longer, if you have a physical job. Discuss this with your physiotherapist or care team.

If after following the above advice, your symptoms have not improved within 6 to 12 weeks, a referral to a physiotherapist may be beneficial. Speak to your GP about a referral.