Shoulder Instability

Written by Brett Harrop


(Also known as Anterior Instability, Posterior Instability, Inferior Instability, Multidirectional Instability, Recurrent Subluxing Shoulder)

What is shoulder instability?

Shoulder instability is relatively common condition characterized by loosening of the connective tissue (ligaments and joint capsule) surrounding the shoulder joint therefore enabling the bones forming the joint to move excessively on each other.

The shoulder joint is a ball and socket joint. The shoulder blade gives rise to the socket of the shoulder, whilst the ball of the shoulder arises from the top of the humerus (upper arm bone). Surrounding the ball and socket joint is strong connective tissue holding the bones together known as the shoulder joint capsule (figure 1) and its associated ligaments (the glenohumeral ligaments). In addition, a group of muscles known as the rotator cuff cross the shoulder joint and actively help to hold the shoulder joint in position increasing the shoulder’s stability.

Shoulder Anatomy for Shoulder Instability
Figure 1 – Shoulder Anatomy for Shoulder Instability

During certain movements of the arm (such as throwing or falling on an outstretched arm), stretching forces are applied to the shoulder joint capsule and ligaments. When these forces are traumatic or repetitive enough, stretching or tearing of the connective tissue may occur. As a result, the connective tissue supporting the shoulder may become loose and unsupportive, allowing the joint to move excessively and resulting in an “unstable” joint. This condition is known as shoulder instability and may result in the upper arm bone (humerus) moving partially or completely out of the socket during certain arm movements (subluxation or dislocation). Shoulder instability normally presents in one shoulder. Occasionally, however, it may exist in both shoulders, particularly in those patients who have general ligament laxity (i.e. loose connective tissue), or in those patients who perform repetitive overhead activities on both sides of the body (such as swimmers).

Causes of shoulder instability

Shoulder instability most commonly occurs following a traumatic incident that partially or completely dislocates the shoulder (such as a fall onto the shoulder, or outstretched hand, or, following a direct blow to the shoulder). This frequently occurs in contact sports such as rugby or Australian rules football, high velocity sports, such as downhill skiing, snowboarding, skateboarding, or in competitive overhead sports such as basketball or water polo. The usual movements involved are a combination of shoulder abduction (side elevation) and excessive external rotation (outer rotation of the humerus) (figure 2) combined with a force to the back of the shoulder or front of the elbow (or both).

Movements involved in a dislocated shoulder
Figure 2 – Movements commonly involved in a dislocated or subluxed shoulder (combined abduction and external rotation)

Shoulder Instability may also occur gradually over time (atraumatically) due to repeated stresses to the shoulder joint associated with repetitive end of range shoulder movements (such as throwing or swimming). This may occur in association with abnormal biomechanics such as poor throwing technique or a faulty swimming stroke and commonly occurs in sports requiring repeated overhead activities such as baseball pitchers, javelin throwers, cricketers, swimmers and tennis players.

Occasionally, shoulder instability may be associated with generalized ligamentous laxity throughout the body. This may be something that is present from birth and is commonly referred to as being ‘double jointed’.

Signs and symptoms of shoulder instability

Patients with shoulder instability may experience little or no symptoms. In atraumatic shoulder instability, the first sign of symptoms may be an episode of the shoulder subluxing (i.e. partially dislocating). In other cases, patients may initially experience shoulder pain or an ache either during, or following, certain activities.

In post-traumatic shoulder instability the patient usually reports a specific painful incident that caused the problem. Commonly the shoulder will have dislocated or subluxed, often with the arm in a position of combined abduction and external rotation at the time of injury (figure 2). Following this incident, the patient may experience pain during certain activities or after these activities with rest (especially at night or the next morning). The patient often reports that the shoulder has never felt the same since.

Patients with shoulder instability will often notice a clicking, clunking or popping sensation within the shoulder during certain movements. There may be a loss of power in the affected shoulder and a feeling of weakness during certain activities (e.g. overhead activity). Patients may also experience tenderness upon firmly touching the front or the back of the shoulder joint and a feeling of apprehension that the shoulder may dislocate with certain end of range movements (particularly the combination of abduction and external rotation) (figure 2). Patients may also experience pain or a sensation of the shoulder joint moving out of place during certain movements or when sleeping on the affected side.

In severe cases of shoulder instability, patients frequently experience recurrent episodes of subluxation or dislocation of the shoulder. This may be associated with shoulder pain and occasionally, a ‘dead arm’ sensation which typically resolves after a few minutes rest. In these instances or in patients with multidirectional instability, the patient may be able to voluntarily sublux or dislocate the shoulder. In more severe cases, relatively minor activities such as yawning or rolling over in bed may result in a subluxation or dislocation.

Diagnosis of shoulder instability

A thorough subjective and objective examination from a physiotherapist is usually sufficient to diagnose shoulder instability. Further investigations such as an X-ray, CT scan, Ultrasound or MRI may be required to assist diagnosis and determine involvement of other structures (such as labral tears, rotator cuff tendinopathy or fractures).

Treatment for shoulder instability

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Prognosis of shoulder instability

Many patients with shoulder instability heal well with an appropriate rehabilitation program and physiotherapy treatment. This may take weeks to months to achieve an optimal outcome. In cases of recurrent shoulder subluxation or dislocation that is unresponsive to conservative treatment, surgical repair of the shoulder joint capsule may be indicated to stabilize the shoulder. This is usually followed by an extensive rehabilitation program lasting many months.

Patients who also have damage to other structures such as cartilage, bone, tendons or nerves are likely to have a significantly extended rehabilitation period to gain optimum function.

Contributing factors to the development of shoulder instability

There are several factors that can contribute to the development of shoulder instability and associated symptoms. These need to be assessed and, where possible, corrected with direction from a physiotherapist. Some of these factors may include:

Physiotherapy for shoulder instability

Physiotherapy treatment for shoulder instability is vital to hasten the healing process and ensure an optimal outcome. Treatment may comprise:

Other intervention for shoulder instability

Despite appropriate physiotherapy management, some patients with shoulder instability require other intervention to ensure an optimal outcome. The treating physiotherapist or doctor can advise on the best course of management when this is the case. This may include further investigations such as X-rays, ultrasound, CT scan or MRI, pharmaceutical intervention, corticosteroid injection, or referral to appropriate medical authorities who can advise on any intervention that may be appropriate to improve the condition. Occasionally, patients may require surgery to repair the loose or torn connective tissue that holds the shoulder in place or to correct other abnormalities associated with the shoulder instability (such as a labral tear or a rotator cuff tear).

Exercises for shoulder instability

The following exercises are commonly prescribed to patients with shoulder instability. You should discuss the suitability of these exercises with your physiotherapist prior to beginning them. Generally, they should be performed 3 times daily and only provided they do not cause or increase symptoms.

Your physiotherapist can advise when it is appropriate to begin the initial exercises and eventually progress to the intermediate and advanced exercises. As a general rule, addition of exercises or progression to more advanced exercises should take place provided there is no increase in symptoms.

Initial Exercises

Shoulder Blade Squeezes

Begin this exercise standing or sitting with your back straight (figure 3). Your chin should be tucked in slightly and your shoulders should be back slightly. Slowly squeeze your shoulder blades together as hard and far as possible provided it does not cause or increase symptoms. Hold for 5 seconds and repeat 10 times provided the exercise is pain free.

Exercises for Shoulder Instability - Shoulder Blade Squeezes
Figure 3 – Shoulder Blade Squeezes

Static Rotator Cuff Contraction

Begin this exercise standing with your back and neck straight and your shoulders back slightly. Keeping your elbow at your side and bent to 90 degrees, push your hand out against the other hands resistance as hard as possible provided it is pain free (figure 4). Hold for 10 seconds and repeat 5 – 10 times on each arm provided there is no increase in symptoms.

Exercises for Shoulder Instability -Static Rotator Cuff Contraction
Figure 4 – Static Rotator Cuff Contraction (right arm)

Shoulder Blade Shrug

Begin this exercise standing with your back and neck straight. Your arm should be at your side, slightly away from your body with your palm facing forwards as demonstrated (figure 5). Slowly elevate your shoulder blade towards your ear as far as possible provided the exercise is pain free (figure 5). Hold for 5 seconds, then slowly return to the starting position and repeat 10 times provided the exercise does not cause or increase symptoms.

Shoulder blade shrug
Figure 5 – Shoulder Blade Shrug (right arm)

Intermediate Exercises

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Advanced Exercises

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Other Exercises

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Rehabilitation Protocol for Shoulder Instability

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Physiotherapy Products for Shoulder InstabilityPhysiotherapy products for shoulder instability

Some of the most commonly recommended products by physiotherapists to hasten healing and speed recovery in patients with shoulder instability include:

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