What is Shoulder Instability?

Shoulder instability is when the shoulder ball is not stabilized by ligaments or cartilage, which means the ball will slide out of the shoulder socket wholly or partially.

Types of Shoulder Instability

There are several reasons why an unstable shoulder may occur. The most common types of instability in the shoulder include:

Dislocation or subluxation: In this case, the shoulder ball, known as the humeral head, moves out of place. This may be a complete or partial dislocation, known as a subluxation and humerus subluxation. This condition is most likely to occur due to an acute injury.
Labral tear: A labral tear or change can lead to a shoulder dislocation since the labrum is the cartilage that supports the head of the shoulder in its position. A labral tear often occurs due to acute injury or impact, but it can also be caused by overuse.
Genetic condition: In some cases, genetic conditions in the body cause weakness and loose ligaments, which may contribute to an unstable shoulder that causes instability.

Shoulder Subluxation vs Dislocation

Shoulder subluxation refers to the partial dislocation of the shoulder. In case of a humeral head subluxation, the ball of the shoulder doesn't completely dislocate from the glenoid fossa but has migrated out of its normal position. When the shoulder's humeral head completely detaches from the glenoid fossa or the socket of the shoulder, it is said to be in complete dislocation. This injury is typically associated with acute trauma or impact, although a subluxation may happen during prolonged repetitive motions that damage muscles, ligaments, and cartilage.

What Causes Shoulder Instability?

Shoulder instability is the shoulder joint's tendency to dislocate or move beyond its normal range. The humerus, or upper arm bone, and the scapula, or shoulder blade, are joined at the shoulder joint, which is a ball and socket joint.

This is a dislocation or subluxation caused by several motions or injuries, such as:

Fall on an outstretched hand with force pushing the humeral head out of shoulder socket
Repetition overhead motion, such as throwing a baseball where the arm goes back behind the body too far
Any movement that draws the humeral head away from the glenoid cavity can elongate or rupture the cartilage (labrum), ligaments, and muscles intended to prevent the humerus from dislocating. If the capsule tears loose from the glenoid rim, the shoulder can become unstable and repeatedly dislocate or subluxate. Shoulder instability is when your shoulder is uniquely predisposed to recurrent dislocation or subluxation.

Chronic Shoulder Instability

Chronic shoulder instability can start occurring at any time. Even people who have never had any history of shoulder problems suffer from chronic shoulder instability following an injury. Some individuals make a full recovery. Due to strained or torn ligaments, cartilage, and muscle, patients whose injuries do not heal properly develop persistent shoulder instability.

Causes of chronic shoulder instability include:

An acute trauma such as a hard blow or fall that dislocates the shoulder and tears or stretches the ligaments. Once the shoulder is loose, it is easily moved, which creates chronic instability.
Repetitive motions such as in an overhead throw loosen the capsule of the shoulder so that it comes out of joint chronically.
A congenital ligamentous laxity, or hyperlaxity, leads to chronic shoulder instability without trauma.

What are the symptoms of Shoulder Instability?

Patients with shoulder instability can also manifest a large variety of symptoms and sensations.

Looseness: Often described by patients as a feeling of giving out, mild shoulder subluxations can result in the patient experiencing a temporary loss of ability to use the joint.
Pain with activity: Shoulder instability can cause pain when performing certain motions or poses of the shoulder.
Weakness: A patient suffering from a shoulder instability case would commonly complain that his shoulder feels weaker than before, especially at activity.
Bruising and swelling: Sometimes shoulder instability worsens, and there will be bruising and swelling.
Reduced range of motion: In a diseased state, an unstable shoulder may not have the same limit of motion as a healthy shoulder.

What is the diagnosis of Shoulder Instability?

Usually, the diagnosis of shoulder instability involves evaluation by a doctor regarding medical examination. A doctor will evaluate weakness also if the range of motion is more limited than is typical or lax. In addition, they will investigate past injuries and shoulder instability in the past.

Additional tests by a doctor may be carried out to have a closer view of the shoulder:

MRI or CT scan
Either an MRI or CT may be performed upon administering dye directly into the shoulder joint; ortho-MRI or arthro-CT
Examination under anesthesia and then arthroscopy of the same

What are the Treatment Options for Shoulder Instability?

Some patients who completely dislocate the shoulder fully recover from this injury and do not suffer from recurrent instability, especially when older and not an athlete or sports participant. Younger patients, and especially athletes, experience recurrent dislocations and subluxations more commonly and usually require surgery to treat the shoulder instability. Learn more about Mass General Brigham's specialized care for shoulder injuries, including shoulder instability.

Non-surgical treatments

Before surgery, a doctor may suggest considering one or more of the following conservative shoulder instability treatment options:

Physical therapy and shoulder instability exercises designed to strengthen the shoulder for several weeks
Activity modification to minimize as much stress as possible on the shoulder and to avoid activities that exacerbate symptoms.
Anti-inflammatory medications to help alleviate inflammation and pain

Shoulder Instability Surgery

If the capsule of the shoulder joint is torn, it can sometimes be reconstructed by reattaching the capsule to the rim of the glenoid. It is referred to as a Bankart repair. The shoulder capsule is exposed by separating the muscles, and if it is discovered that the capsule has ripped away from the bone, the glenoid rim is punctured three times. The stitches are passed to each hole in the capsule, then they get tied, fixing the capsule to the bony rim of the glenoid. The capsule heals into the bony rim and prevents the re-dislocation of the shoulder. It takes some months to recover back to bone for the capsule. During this period, strenuous motions of the shoulder should be avoided in order not to disturb the stitches from unraveling.

This can also be done with the help of an arthroscope without opening the shoulder. In cases of a small tear and low subsequent demands in the shoulder, this will be a good alternative. If the tear is large and the shoulder very unstable, open repair is stronger, especially in athletes.

The bankart repair is successful in about 97%. Recurrent instability after repair appears to be significantly increased if there is a fracture of the glenoid rim (Bankart lesion) and compression fracture of the humeral head (Hill-Sachs lesion). Two nerves are at risk because they are in proximity to the operative field, but they are rarely damaged. Risks of the procedure do exist, as they do for all surgical procedures. The infection rate is less than 0.5%. The shoulder could lose some motion post-surgery if the shoulder needs over-tightening because of excess laxity.

What is the recovery time from shoulder subluxation?

Shoulder subluxation may have follow-through therapy with non-surgical treatment to show recovery after a couple of months.

Is shoulder instability a severe condition?

Typically, the severity of shoulder instability in the short term is associated with loss of strength or motion in the shoulder and subjective pain levels. Still, if left untreated, this can lead to further degenerative shoulder pathologies.

How long will rehabilitation after surgery take?

The recovery after surgery might take as long as six months to recover the motions, and sometimes, it may take up to one year to recover fully from high-intensity activities.

Shoulder instability can it be self-managed?

Most minor cases of shoulder instability resolve without much inconvenience; however, they heal on their own with appropriate therapy and activity modification. In the case of moderate instability, most will require surgery.