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Shoulder Instability

(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 and its associated ligaments. In addition, a group of muscles known as the rotator cuff cross the shoulder joint and collectively help to hold the shoulder joint in position increasing the shoulder's stability.
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 subtly 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 football. The usual movements involved are a combination of shoulder abduction (side elevation) and excessive external rotation (outer rotation of the humerus).
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, 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) or shoulder pain or 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. 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 usually 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). Patients may also experience pain or a sensation of the shoulder joint moving out of place 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 physician 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 tendonitis or fractures).

Treatment for shoulder instability
Most cases of shoulder instability respond well to conservative treatment involving intensive rehabilitation exercises and appropriate physical therapy. Treatment also requires careful assessment by the physical therapist to determine which factors have contributed to the development of the condition (particularly in the case of atraumatic instability), with subsequent correction of these factors.
The success rate of treatment is largely dictated by patient compliance. One of the key components of treatment is that the patient rests sufficiently from ANY activity that increases their pain until they are symptom free. Activities which place large amounts of stress through the shoulder joint should also be minimized, these may include: throwing, swimming, bench press, dips or military press. Exercising into pain must also be avoided. This allows the body to begin the healing process in the absence of further tissue damage.
Ignoring symptoms or adopting a 'no pain, no gain' attitude is likely to lead to the problem becoming chronic. Immediate, appropriate treatment in patients with shoulder instability is essential to ensure a speedy recovery. Once the condition is chronic, healing slows significantly resulting in markedly increased recovery times.
An intensive exercise program is essential to ensure an optimal outcome in all patients with shoulder instability. This primarily involves strengthening of the shoulder stabilizers (rotator cuff muscles), the scapular (shoulder blade) stabilizing muscles and appropriate postural exercises. The strengthening program usually has a particular emphasis on strengthening the muscles that oppose the direction of the instability. Certain stretches should be avoided in patients with this condition as this may contribute to further instability. The treating physical therapist can advise which exercises are most appropriate for the patient and when they should be commenced.
Sporting modification and biomechanical correction play an important part in the treatment of shoulder instability (e.g. throwing technique correction, swimming stroke correction and tennis serve correction). In addition, a graduated return to sport or activity program under the direction of a physical therapist is also required in the final stages of rehabilitation to recondition the shoulder for sport or activity in a safe and effective manner. Shoulder taping techniques may be used in this stage to protect and stabilize the shoulder (particularly when returning to contact sports).
In some cases of post-traumatic shoulder instability, conservative measures consisting of an intensive strengthening program may be unsuccessful in relieving the symptoms associated with instability. In this case surgical treatment may be indicated.

Prognosis of shoulder instability
Many patients with shoulder instability heal well with an appropriate rehabilitation program and physical therapy 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 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:
  • history of previous shoulder subluxation or dislocation
  • inadequate rehabilitation following a shoulder dislocation
  • intensive participation in sports or activities placing the shoulder at risk of developing instability
  • muscle weakness (particularly of the scapular stabilizers and rotator cuff)
  • muscle imbalances
  • poor posture
  • shoulder joint hypermobility
  • general ligamentous laxity
  • abnormal biomechanics or sporting technique (such as poor throwing technique or faulty swimming style)
  • thoracic spine stiffness
  • muscle tightness (affecting posture)
  • poor core stability
  • inappropriate training or technique
  • change in training conditions
  • inadequate warm up
Physical therapy for shoulder instability
Physical therapy treatment for shoulder instability is vital to hasten the healing process and ensure an optimal outcome. Treatment may comprise:
  • progressive exercises to improve rotator cuff strength, shoulder strength, shoulder blade stability, posture and core stability
  • biomechanical correction (e.g. correction of throwing technique, swimming stroke, tennis serve, weight lifting technique etc)
  • soft tissue massage
  • electrotherapy (e.g. ultrasound)
  • protective taping
  • joint mobilization (thoracic spine or neck)
  • dry needling
  • ice or heat treatment
  • education
  • activity modification advice
  • postural correction
  • clinical Pilates
  • anti-inflammatory advice
  • devising and monitoring a return to sport or activity plan

Other intervention for shoulder instability

Despite appropriate physical therapy management, some patients with shoulder instability require other intervention to ensure an optimal outcome. The treating physical therapist 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