Glenohumeral Joint Instability

The glenohumeral joint (GH) is a ball and socket joint that includes a complex, dynamic, articulation between the proximal humerus (“ball”) and the glenoid (“socket”) of the scapula. The static and dynamic stabilizing structures allow for extreme range of motion in multiple planes, that predisposes the joint to instability events. Shoulder instability often occurs when the capsule (lining of the shoulder joint), ligaments, or labrum becomes stretched, torn, or detached from the glenoid, commonly after shoulder trauma or repetitive motion. A genetic condition can also cause looseness and weakness in the joint. Exercise programs that aim to strengthen the rotator cuff and scapular muscles are often the primary treatment for instability, where full range of motion usually returns after 6-8 weeks.


Structurally a ball and socket joint, that involves the humeral head with the glenoid cavity of the scapula, and it represents the major articulation of the shoulder girdle. The joint capsule and ligaments provide a passive restraint to keep the humeral head compressed against the glenoid. As one of the most mobile joints, the GH joint has stabilising elements, that are divided into static (capsule-labro-ligamentous complex) and active (rotator cuffs and bicep tendons).


The symptoms of Glenohumeral Joint Instability include but may not be limited to:

  • Pain, tenderness, swelling, and/or bruising.
  • A loose feeling, or hearing a “pop” in the shoulder joint.
  • Repeated shoulder dislocation.
  • Tingling or burning sensation in the lower arm and hand.
  • Localised numbness of the skin overlying the deltoid muscle.
  • Decreased range of arm/shoulder motion.


Glenohumeral joint instability can occur following a traumatic accident such as a fall or collision. It can also occur without significant trauma or injury, which is often genetic from those with hypermobility or connective tissue problems, or from a development of laxity in tissues of the shoulder joint. Other causes can be from repetitive motions, particularly from throwing sports, causing the shoulder to stretch over time, where normal muscle control is lost.


A physical examination can confirm the impression obtained from the history and help to determine if the shoulder is loose or unstable. Radiographs or imaging, such as X-rays, MRI, or a CT scan can help to provide confirmation of traumatic glenohumeral instability present from the damaged bones, cartilage, and rotator cuff. Mobility may be restricted for two weeks, followed by physical therapy to strengthen the muscles that stabilises the shoulder.


Polar Type I (structural instability) – typically present with a positive apprehension (anterior direction) associated with rotator cuff weakness. Posture, single leg balance, and scapula control are often disturbed. Can begin to exhibit signs of poor scapula control, abnormal muscle activation, and altered trunk stability and balance, when moving towards type II and III poles.

Polar Type II – (atraumatic instability) – present with positive anterior apprehension test, with increased laxity and excessive external rotations, and muscular balance

Polar Type III – (neurological dysfunctional or muscle patterning) – shows abnormal activation of large muscles and suppression of the rotator cuff. Mostly occurs with a history of easy shoulder dislocation.


Treatment usually begins with physical therapy, designed to strengthen the shoulder, and maintain the joint in position.

Restricting activity that includes overhead motion may be advised to reduce symptoms. Full range of motion usually returns after 6-8 weeks.

If less invasive treatments don’t work, and in severe instances, open surgery is often necessary, where an incision is made over the shoulder and the muscles are moved to access the joint capsule, ligaments, and labrum. After surgery, full recovery often takes 4-6 months, and in some cases up to 12 months. At this stage some deep tissue massage and scar tissue work may be necesary!


  • Shoulder flexion (lying down)
  • Shoulder blade squeeze
  • Resisted rows
  • Internal rotator strengthening exercise
  • External rotator strengthening exercise (with arm abducted 90°)
  • Standing row (with resistance band)


Glenohumeral Joint Instability (GJI) is a condition that occurs when the ball and socket joint of the shoulder become dislocated or partially dislocated due to trauma or other underlying conditions. GJI can result in pain, weakness, and limited range of motion, making it difficult for people to perform their daily activities. In severe cases, surgery may be required to treat the condition. However, prevention is always better than cure, and there are several steps that individuals can take to prevent GJI.

Strengthen the Rotator Cuff Muscles:
The rotator cuff muscles are a group of muscles that attach the shoulder blade to the humerus bone and help stabilize the shoulder joint. Strengthening these muscles can help prevent GJI. Exercises that target the rotator cuff muscles include external and internal rotation exercises, scapular stabilization exercises, and shoulder blade squeezes.

Improve Shoulder Mobility:
Limited shoulder mobility can lead to increased stress on the shoulder joint, which can increase the risk of GJI. Stretching exercises that target the shoulder joint, such as shoulder circles and shoulder flexion stretches, can help improve shoulder mobility and prevent GJI.

Maintain Good Posture:
Poor posture can contribute to shoulder instability and increase the risk of GJI. Individuals should aim to maintain good posture by keeping their shoulders back and down and their chest open. Practicing good posture can help improve shoulder alignment and stability.

Avoid Overuse Injuries:
Overuse injuries can cause wear and tear on the shoulder joint, leading to increased instability and a higher risk of GJI. To avoid overuse injuries, individuals should practice proper form and technique when performing exercises and avoid repetitive overhead movements.

Wear Proper Protective Gear:
Individuals who participate in contact sports or activities that involve the risk of shoulder injuries should wear proper protective gear, such as shoulder pads or braces. Protective gear can help absorb the impact of a fall or collision, reducing the risk of GJI.

In conclusion, preventing GJI requires a combination of strengthening exercises, stretching, good posture, injury prevention strategies, and protective gear. By following these steps, individuals can help reduce the risk of GJI and maintain a healthy and stable shoulder joint. It is important to consult with a healthcare professional before starting any new exercise program or if experiencing any shoulder pain or discomfort. If you are unsure what to do, please contact us and one of our Personal Trainers or Sports Therapists can help.