"I was taking this shot and the opponent tried to stop me by pulling my arm. When it happened it was very painful and it felt like something happend in the shoulder. Now I don't have that much pain anymore but I have this sensation that my shoulder is going to pop out when I have my arm in certain positions"
Shoulder instability can present itself in various forms within overhead sports due to the repetitive nature of throwing, which places considerable demand on shoulder stability. This repetitive motion can lead to acquired instability, including issues like SLAP lesions. Additionally, some players may have congenital hypermobility, which, while beneficial for shoulder mobility in sports like handball, can also become a disadvantage if the athlete struggles to control it, especially during the cocking and acceleration phases of throwing. Finnaly, shoulder instability can also be caused by trauma where the athlete dislocate or subluxate their shoulder.
Mechanisms
Instability can be classified into three general types based on its cause: AIOS (Acquired Instability due to Overstress Syndrome), AMBRI (Atraumatic, Multidirectional, with Bilateral laxity, where Rehabilitation is the first choice and Inferior capsular shift surgery is a secondary option), and TUBS (Traumatic, Unidirectional instability often accompanied by a Bankart lesion, which usually requires Surgery).
In contact sports like handball, traumatic instability is a potential concern. Glenohumeral dislocation or subluxation may occur from falls, often when the arm is extended. Instability in the acromioclavicular joint is common when the lateral shoulder hits the ground. During the cocking phase of a throw, anterior instability may develop if arm movement is obstructed. This type of instability poses greater challenges due to its occurrence in the throwing position, often leading to a more serious prognosis. In some cases, these injuries may affect the brachial plexus, further complicating the issue.
Assessment
When assessing glenohumeral joint stability, it is crucial to recognize that a high degree of joint laxity or “play” does not necessarily indicate instability, nor does a lack of laxity rule it out. Laxity refers to the shoulder’s capacity for movement or translation in multiple directions, whereas instability is the patient’s subjective experience of feeling insecure or unstable in the joint. This instability may be due to weak motor control, reduced shoulder strength, or even structural instability.
Two primary tests used to evaluate shoulder joint laxity are the Load and Shift test, which assesses anterior and posterior translation, and the Sulcus Sign test, which checks for inferior translation. While these tests measure laxity, which may or may not be linked to injuries, a patient’s report of discomfort or identifying “their problem” during testing can provide clinically relevant insights beyond the degree of movement observed.
For posterior instability, the Load and Shift test can be modified to examine posterior translation, or the Posterior instability test can be performed. In this test, the player lays supine on the treatment table while the examiner stabilizes the humeral head and apply an posterior load along the humeral head. A positive result is indicated if the player experiences discomfort. Often the examiner can feel the humeral head gliding up in the glenohumeral rim causing posterior subluxation in an unstable shoulder.
The Apprehension Test or Fulcrum Test is the most widely used method to assess anterior instability. In this test, the player lies supine, and the examiner elevates the arm to a 90-90 position (90° abduction and 90° external rotation), gradually moving the arm posteriorly. To further challenge stability, the examiner may push the humeral head forward (Fulcrum Test). A positive test occurs when the player reports apprehension or a sensation of impending dislocation. During the Apprehension Test, the examiner can apply a backward force (Relocation Test), which moves the humeral head posteriorly. If the instability sensation decreases, this suggests anterior instability. However, this backward force also externally rotates the scapula, reducing the scapulohumeral angle and easing compressive stress on the posterior labrum, capsule, and rotator cuff. Thus, pain relief in the Relocation Test does not necessarily confirm instability.
Although it is common to conduct the Apprehension Test at 90° abduction, athletes often throw with the arm positioned above or below this angle. Therefore, it may be beneficial to perform the test at various angles, from as low as 45° (Castagna’s Test) to as high as 160°, to capture the full range of potential instability. Additionally, the patient may be able to identify the specific position where they feel unstable or experience pain, helping the examiner pinpoint the range of motion where instability is likely to occur.
These instability provocation tests (apprehension and posterior instability tests) should also be performed actively, with the athlete engaging in an isometric contraction in each test position. For example, during the apprehension test, the athlete performs an isometric internal rotation, and in the cross-body position, an isometric horizontal abduction. This approach helps assess how well the athlete can stabilize the shoulder during these movements. If instability is present, the athlete is often hesitant to perform the contraction and may describe the shoulder as feeling weak, wobbly, unstable, or untrustworthy
Management
The rehabilitation approach for an unstable shoulder can vary based on the underlying cause, the severity of the instability, and whether treatment is surgical or conservative. Generally, strengthening of the shoulder and scapular muscles is essential for all cases of shoulder instability. To enhance joint stability, however, closed-chain exercises are often preferred by the athlete initially, keeping the shoulder in positions that minimize feelings of instability. Many individuals with shoulder instability experience anxiety, fear, and movement avoidance, so it is crucial to emphasize motor control and coordination exercises, especially in the early stages of rehab. Often, the athlete is limited less by pain and more by a sensation of instability. Once we identify positions or movements that do not aggravate this feeling of the shoulder 'popping out,' we can increase the load fairly quickly.
The closed kinetic chain exercises may later progress to include challenges such as unstable surfaces, perturbations, or additional cognitive tasks like counting backward, which increase the difficulty before transitioning to open-chain and sport-specific exercises. The final phase of the rehabilitation should include sport specific demands in that specific shoulder position where the athletes experiences their instability e.g., in throwing position or in different defence positions for a handball player.
To gauge psychological readiness for progression and return to sport, the Tampa Scale for Kinesiophobia can be valuable, especially in cases involving instability. The rates of recurrence and successful return to sport (RTS) vary significantly depending on the sport, the athlete’s position, the type of instability, if it is the dominant or non-dominant shoulder and whether surgery was involved. Recurrence rates range from 27% to 92%, with younger athletes in contact sports, particularly males, facing the highest risk of recurrent dislocations.
Summary
Shoulder instability in overhead athletes is often caused by repetitive throwing motions, congenital hyper mobility, or traumatic events, leading to challenges in control and stability, especially in vulnerable throwing positions. Effective management combines targeted strengthening, stability-focused exercises, and assessments to gauge stability and readiness for return to sport. Recovery success varies, depending of type of sport, dominant or non.dominant arm and age, with recurrence rates higher in younger athletes involved in contact sports
As we conclude this series, we have examined the most common shoulder problems encountered by overhead athletes. In our next blog post, we will wrap up the series by focusing on the critical decisions involved in returning to sport after a shoulder injury in overhead athletes. Will explore how to determine—or at least make an educated guess—when an athlete is truly ready to resume activities, specifically focusing on the challenge of knowing when someone can safely throw a ball at speeds exceeding 100 km/h. Stay tuned as we delve into the criteria and assessments that help ensure a successful and secure return to peak performance.
