Multidirectional Instability (MDI) of the Shoulder (Gleno-Humeral Joint)

Background Anatomy

The glenohumeral joint of the shoulder is a ball-in-socket joint between the head of the humerus (the ball part), and the glenoid (the socket part). This joint relies a lot on the muscles, ligaments, and other soft tissue structures for stability, because the bony part of the joint is actually not very deep at all. In fact, without any help from its ligaments and muscles, this joint is analogous to a golf ball sitting on a tee. The great thing about this joint is that it allows for a lot of movement. However, there is a trade-off between stability and mobility, and in the shoulder, this trade-off favours mobility.

What is Multidirectional Instability (MDI)?

Multidirectional instability of the shoulder is a condition where the head of the humerus has difficulty staying centered in the glenoid. There is excessive movement and poor control of the joint in multiple directions.

What causes MDI?

MDI often presents without any acute trauma, although there may be some gradual micro-trauma that has developed over time. This excessive joint mobility may also be due to looseness in the joint capsule and ligaments around the glenohumeral joint, and weakness or poor control of the muscles around the shoulder.

Who gets MDI?

Generally people in their teens up until their late twenties are most likely to experience symptoms of MDI. This is partly because as we age, our tissues tend to get stiffer and less flexible. MDI only accounts for approximately 10% of all shoulder instabilities, however 50% of those with MDI are athletes. Gymnastics, swimming, and baseball are some examples of sports where the prevalence of MDI is higher than in the general population. People involved in work with repetitive overhead positions, and people with a history of previous shoulder subluxation or dislocation are also at increased risk for developing MDI.

What are some common signs & symptoms associated with MDI?

• General shoulder fatigue
• Vague location of pain in the shoulder
• Feeling like the shoulder is unstable, possibly with recurrent subluxations
• Arc of pain lifting the arm overhead
• Fear of moving the shoulder in particular directions
• Presence of clicking, clunking, and/or popping noises with shoulder movements
• Aggravation of pain and/or numbness/tingling in the shoulder and/or down the arm with carrying heavy objects, pushing heavy doors, push-ups, and throwing activities
• Achiness in the shoulder at night

What treatment is available, and what is the prognosis for MDI?

Physiotherapy rehabilitation is the preferred first line of treatment for MDI. A physiotherapy program for MDI will often involve postural education, activity modification, supportive taping, pain relieving modalities and manual therapies, as well as an individualized exercise program to help target key areas of weakness which need to be addressed. The majority of patients who respond well to physiotherapy should see significant improvements within three months of starting a physiotherapy program for MDI.

The prognosis for MDI rehabilitation is generally good, although it is dependent on both age and activity level. Younger people, and those involved in demanding sports tend to have a poorer prognosis. In cases where disabling symptoms persist and conservative management is unsuccessful, there are surgical options that can be considered. However, participation in demanding sports will also negatively affect the prognosis for surgical interventions for MDI.

If you are concerned that you might have multidirecitonal instability, or if you have any questions or concerns about this condition, please do not hesitate to contact us. You can book an assessment with one of our registered physiotherapists, who are very knowledgeable about this condition. We can answer your questions and develop a treatment plan to help get rid of your pain, improve your function, and achieve your goals.

Written By: Reanna Montopoli, Registered Physiotherapist