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Stability vs. Mobility: Why the Shoulder is Susceptible to Dislocation

Posted by Douglas W. Stoddard MD, M Sp Med, Dip Sport Med, ES on 29 June 2015
Stability vs. Mobility: Why the Shoulder is Susceptible to Dislocation

Day-to-day activities and most sports require our upper bodies to move against little external resistance. Whether it's throwing, making a tackle on the field, or performing a golf swing, we need adequate mobility in our shoulders.

The shoulder is one of the most mobile joints in our body. However, it sacrifices stability for this needed mobility. In this blog post, we'll explore the concept of shoulder dislocation and subluxation, as well as the factors that contribute to shoulder stability and the rehabilitation for shoulder instability.

The Difference Between Dislocation and Subluxation:

Dislocation is when a joint is forced out of its resting position, and remains dislodged.

Subluxation is when a joint momentarily slides out of its resting position, but quickly moves back into place. Subluxation may occur after a previous dislocation or may progress to a dislocation.

You Subluxed Your Shoulder If:

  •    You've fallen and had your arm fully outstretched behind you.
  •    You feel your shoulder moving in and out of the joint while walking or performing light activities.
  •    Your arm feel weak when you try to lift it up above your shoulders.
  •    You have sharp pain in your shoulder when throwing or reaching out sideways.

Categories of Shoulder Instabilities:

  •   Anterior (front of the joint and most common)
  •   Posterior (back of the joint)
  •   Multi-directional (more than one area of the joint)

Five Reasons Your Shoulder Doesn't Dislocate:

  1. The shoulder socket is normally angled upwards, providing a supporting ledge for the arm bone.
  2. The cartilage ring deepens the surface area of contact so that the arm bone has a more supportive surface to rest on.
  3. Ligaments surround the entire joint from top to bottom and front to back. Like elastic bands, they're extremely strong and help prevent any excessive movement between the arm bone and the socket.
  4. A thin layer of fluid exists between the arm bone and the socket which creates a vacuuming effect between the two bones.
  5. The rotator cuff muscle maximizes joint compression by keeping the arm bone centered into the socket.

Shoulder dislocations can damage any of the above components leading to a decrease in activity, and resulting in chronic instability.

How to Rehabilitate an Unstable Shoulder:

  • Regaining strength and control of the shoulder blade in order to achieve an optimal resting position of the scapula.
  • Restore functional strength of the rotator cuff.
  • Perform postural exercises to maintain proper positioning of the scapula.

If conservative treatment fails, surgical intervention is sometimes required for traumatic shoulder instabilities.

If you're experincing any shoulder pain, SEMI's physiotherapists have got your back. To learn more about our sports physiotherapy services and how we can help, contact us today at 1-855-572-9177.


Steve Wong,  BHK, BSc PT, MCPA.

Printed: August 2005
Copyright ©2005 SEMI

Author: Douglas W. Stoddard MD, M Sp Med, Dip Sport Med, ES
About: Dr. Douglas Stoddard is a sports medicine physician and is the Medical Director of the Sports & Exercise Medicine Institute (SEMI). After receiving his medical degree from the University of Toronto, he trained in Australia at the Australian Institute of Sport in Canberra, obtaining his Master Degree in Sports Medicine. He is also a diplomat of the Canadian Academy of Sport and Exercise Medicine and has his focussed practice designation in Sport Medicine from the Ontario Medical Association. Dr. Stoddard is a consultant to the Canadian Military and has consulted with well over 30,000 unique patients in his career. Dr. Stoddard is constantly searching for new and promising therapies to help SEMI patients, and is responsible for developing the RegenerVate Medical Injection Therapy Program. He is married and the proud father of two boys, is an avid triathlete and occasional guitar player.
Tags: Prevention Upper body Treatment options


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