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How Do Shoulder Dislocations Occur?

July 11, 2022

The thought of shoulder dislocations can be scary, especially among young athletes who are most susceptible to this type of injury and since the general recurrence rate of dislocations is so high. This blog talks though what happens in a shoulder dislocation and what the rehab may look like. 

The shoulder anatomy 

The shoulder joint is formed by the humerus (upper arm bone) that fits into the groove of the shoulder blade like a ball and socket, making it the most mobile joint in the body, which is also the reason why shoulder dislocations are so common. 

There are some passive and dynamic stabilizers of the shoulder as it moves through its various ranges to maintain the head of the humerus in its joint: 

Dynamic:

  • Rotator cuff muscles (supraspinatus, infraspinatus, subscapularis, teres minor) 
  • Deltoid muscle 
  • Periscapular muscles 

Passive:

  • Three glenohumeral ligaments 
  • Coracohumeral ligament 
  • Glenoid labrum 


 

 

Which shoulder dislocation is more common? 

There are two directions that the shoulder can dislocate: anteriorly (forwards) and posteriorly (backwards). The more common of the two, the anterior dislocation of the shoulder, occurs from sudden or excessive outward rotation and/or extension with the arm in an overhead position. A force applied to this vulnerable position of the shoulder, often during contact sports, pushes the head of the humerus forwards and out of its socket, resulting in the dislocation. Some people are born with instability in their shoulders as well, allowing them to pop their shoulders out of their sockets as a party trick.  

The anterior dislocation of the shoulder amounts to 96% of all shoulder dislocations and it can vary from a full dislocation to a minor subluxation (partial dislocation) and may even involve other injuries such as a labral or capsular injury, a fracture to the glenoid rim (Bankart lesion) or an impaction fracture to backside of the humeral head (Hill-Sach’s lesion). 

On the other hand, the posterior dislocation of the shoulder accounts for less than 5% of all shoulder dislocations, typically caused by an external force to the front of the shoulder, a fall onto an outstretched hand, motor vehicle accident or even seizures. Due to the traumatic nature of injury, posterior dislocations are often accompanied by other complications.

Do I need surgery?

Many factors are involved with determining whether surgical intervention is required, such as recurrence, age, future plans and timing during the sporting season and the extent of injury. However, surgery is generally not considered until after a failed course of conservative management as most people will achieve an adequate recovery with immobilization and exercise. 

Once dislocated, the ligaments holding the humeral head become stretched and can lead to chronic instability and a higher risk of redislocation. The recurrence rate after the first dislocation can vary between various populations: 

  • 72-100% in people <20 years of age
  • Up to 80% in people between 20-30 years of age
  • Up to 22% in people >50 years of age 
  • Recurrence rate can be as high as 92% in young athletes

The evidence is limited to tell us whether surgery is better than conservative management in each type of population and there are many variable factors involved with undertaking surgery to stabilize the shoulder. However there are several studies that support surgical treatment in young adults engaged in highly demanding physical activities. 

How to avoid surgery after shoulder dislocations 

Non-surgical management of a shoulder dislocation involves resting the arm in a sling for 3-6 weeks (time depending on the amount of pain and timeframes for return to activity) followed by gentle range of motion exercises to increase the pain-free range of the shoulder. Shortly after getting out of a sling, it will be very important to begin activating and strengthening the dynamic shoulder stabilizers and muscles used for scapular control. 

Sport or task specific exercises should commence once range of motion and strength is similar to the non-affected side and exercises can be progressed to work in more vulnerable ranges of the shoulder to ensure adequate control and strength. 

No one likes to go under the knife if it can be avoided. At StudioXphys, we have skilled physiotherapists who can guide you through a tailored rehabilitation and exercise program to strengthen the shoulder, whether it is your goal to return to your sport, work activity, daily tasks without pain or instability.

Jun Sugio 

Physiotherapist (BPthy, APA, AHPRA)

References: 

Handoll, H., & Al-Maiyah, M. (2004). Surgical versus non-surgical treatment for acute anterior shoulder dislocation. Cochrane Database Of Systematic Reviews, 2010(5). https://doi.org/10.1002/14651858.cd004325.pub2

Polyzois, I., Levy, O., Dattani, R., Gupta, R., & Narvani, A. (2016). Traumatic First Time Shoulder Dislocation: Surgery vs Non-Operative Treatment. The Archives Of Bone And Joint Surgery. Retrieved 6 July 2022, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4852033/.

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