The shoulder is a complex joint that allows for a large amount of movement in multiple planes. What we sacrifice for all of this movement in the shoulder is stability. Stability in the shoulder joint comes from both static and dynamic factors. Static stability refers to the boney anatomy of the glenoid fossa, humeral head and the labrum as well as the ligaments that act on the shoulder joint complex. Dynamic stability refers to the neuro-muscular control of the shoulder complex which includes the scapula (shoulder blade).
There are two types of instabilities in the shoulder joint complex.
Traumatic Instability: With this instability there has been a clear mechanism of injury, such as with a shoulder dislocation, usually due to external force being placed on the glenohumeral joint (ie. fall)
Multi-Directional Instability (MDI): The gleno-humeral joint is lax or “loose” and therefore can cause episodes of instability. There has been no mechanism of injury, trauma or external forces that creates an MDI. Someone might complain of ‘clunking’ or ‘shifting’ in their shoulder.
Many of these injuries or pathologies respond well to conservative management with physiotherapy, which would include a strengthening program.
A study published in the American Journal of Sports Medicine compared two rehab protocols (Watson and Rockwood) for MDI’s and found the following:
12 weeks of the Watson program showed more favourable outcomes when compared to the Rockwood at both 3 and 6 month follow ups.
What is interesting from comparison of the two protocols is that the Watson protocol has more of a focus on retraining scapular motor control initially and then progressing into strengthening exercises of the rotator cuff and deltoids and working into sport specific exercise. The scapula is critical in creating stability for the shoulder joint complex, so an exercise program focussing on the dynamic control and scapular stabilization exercises is key in a successful rehab program of any shoulder instability. Please consult with a physiotherapist regarding exercises if you are experiencing any shoulder instability.
Warby SA, Ford JJ, Hahne AJ, Watson L, Balster S, Lenssen R, Pizzari T (2018) Comparison of 2 Exercise Rehabilitation Programs for Multidirectional Instability of the Glenohumeral Joint: A Randomized Controlled Trial, Am J Sports Med, 46(1):87-97.