Shoulder Instability: A Cool Party Trick or Injury? Causes, Examination, & Treatment

Written By: Ashley Bowser, PT, DPT


If you are one of those people who can easily locate and dislocate their shoulder as a party trick you may be wondering if this is normal.  The simple answer is unfortunately no.  Even if you don’t have pain, you could be predisposing yourself to future injury or if left unaddressed.  The good news is that there are many ways to improve stability at your shoulder through physical therapy and exercise. 

Shoulder Complexity

The shoulder is an extremely complex joint and is unsurprisingly one of the most commonly treated in orthopedics.  One of the most challenging conditions to treat is shoulder instability.  The shoulder is comprised of the acromioclavicular (AC) joint, sternoclavicular (SC joint), glenohumeral (GH) joint, and scapulothoracic joint.  The SC joint is the only bony attachment of the upper extremity to the skeleton, and the glenohumeral joint is a ball-and-socket joint.  The head of the humerus (top of the arm) glides multi-directionally within the glenoid labrum which is part of the scapula.  The problem with this joint is that it’s already predisposed to instability due to the large surface area of the humeral head and small glenoid fossa.  Therefore, it relies on the passive support of the glenoid labrum, ligaments surrounding the GH joint, and negative intra-articular pressure.  The rotator cuff muscles also attach to the humeral head within the glenoid fossa, and by contracting they help to maintain a central position of humeral head in the glenoid limiting excessive translation.  These muscles also blend with ligaments of the glenoid labrum, so muscle contractions can provide additional stability by tightening these structures. To complicate matters the scapulothoracic joint is a floating joint where the scapula glides along the rib cage.  There is only a small amount of upward translation at the GH joint with the rest of the movement coming from coordinated movement of the scapula.  The scapula acts dynamically to control the position of the glenoid and harmonious co-contraction of the rotator cuff muscles.  This requires adequate proprioception and neuromuscular control, as well as, strength in key muscles.  Usually it is a disturbance in the balanced teamwork of global muscle movers and fine-tuning stabilizing muscles, in addition to a delay in delivery of proprioceptive signals and muscle response that results in shoulder injury.  

How Shoulder Instability Occurs

Your shoulder may become unstable due to a traumatic injury or an Atraumatic injury.  Traumatic injuries are specific, sudden disruptions to tissue integrity, and usually occur with falling on an outstretched arm.  This often results in injury to the static stabilizers of the shoulder (ex: ligaments, glenoid, capsule).  If you are a shoulder party trick person you may be wondering how this applies to you if you haven’t fallen or have been able to do this all your life.  The answer is that instability can also occur overtime or can be related to congenital defects.  You may have been born with increased laxity of static structures due to increased collagen elastin, decreased size of the glenoid, bony abnormalities, and decreased retroversion (glenoid facing more laterally or posteriorly than normal).  Another possibility is that you have developed microtrauma in stabilizing tissues due to faulty biomechanics, over training, poor technique, poor motor control, decreased flexibility in certain areas, or skeletal malalignment.  This is very common in sports or activities that require reaching out to the side and rotating externally (ex: pitching).  The mechanism of injury will determine treatments provided.  More often than not patients experience anterior dislocations due to posterior capsule tightness, weakness at the rotator cuff, and glenoid position/integrity. 

Shoulder Instability Presentation

Your doctor or physical therapist will evaluate to see what the underlying cause of your instability is. They will ask you about clicking, pain, dead arm, impingement, and joint motion.  They will perform special tests to see if you are apprehensive or demonstrate excessive joint motion.  Furthermore, scapular dyskinesis or abnormal positioning during rest or motion will reveal signs of rotator cuff/muscle weakness, nerve damage, or imbalance in muscles.  Finally testing will be performed to evaluate neuromuscular control, rhythmic stability, and proprioception.  These results will help formulate the course of treatment. 

Treatment

Treatment will vary depending on the mechanism of injury and deficits found during your examination.  Traumatic injuries are often painful and patients have apprehension.  Therefore, treatment incorporates immobilization in a sling and early controlled PROM.  Initially exercises tend to be very mild.  A traumatic injury treatment incorporates focus on early proprioception training, dynamic stabilization drills, neuromuscular control, rotator cuff strengthening, and scapular muscle exercises.  Usually the exercises can be more aggressive.  

In extreme cases surgical intervention may be required, including open capulsar shift or capsulorrhaphy.  Following surgery the shoulder will be mobilized for about 3 weeks before gradual PROM and exercise progression are administered. 

What Does all This Mean?

The shoulder is very complex, and a lot of information is required to understand it.  If you have any symptoms consistent with shoulder instability including clicking, pain, apprehension, numbness, or feelings like it comes in and out of socket don’t hesitate to come see us at Austin Sports Medicine.  Instability often becomes a chronic issue and can worsen over time and it is best to treat it as soon as possible. Our therapists and doctors are highly experienced in treating shoulder instability through exercise and surgery, and will get you back to the lifestyle you love!

Common PT Exercises

Serratus punch or Push up Plus
Body blade or Wall Ball
PNF Patterns
Scapular Strengthening
Shoulder External/Internal Rotation 

 

Global Movers of the Shoulder Fine-Tuning muscles of the Shoulder 
Long Head of the Bicep Supraspinatus (rotator cuff)
Coracobrachialis Infraspinatus (rotator cuff)
Teres Major Subscapularis (rotator cuff)
Rhomboids Teres Minor (rotator cuff)
Latissimus Dorsi
Trapezius
Levator Scapula
Deltoids
Serratus Anterior
Pectoralis Major/Minor
Muscles that stabilize the GH joint
Supraspinatus Prevents superior humeral head translation
Infraspinatus/Teres Minor Prevents superior/posterior humeral head translation
Subscapularis Prevents anterior/superior humeral head translation

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