"I have had shoulder pain on and off for a period and for the last couple of weeks it has become worse. It is now painful on the top/back of my shoulder when I try to throw and I can't throw as hard as I used to. Sometime the arm feels dead!"
This is a typical history for a thrower with inside shoulder impingement. Most often, there isn’t a specific onset; rather, the problem develops gradually over time, with symptoms increasing in intensity and changing in nature. Typically, the athlete continues to push through the discomfort and only seeks care once their performance is impacted—such as when they can no longer throw as hard as before.
Mechanisms
Inside, or internal, impingement is a condition where posterior-superior shoulder pain arises due to compression of the posterior-superior rotator cuff against the back of the glenoid during the cocking phase of throwing. This condition, commonly experienced by overhead athletes, often results from a combination of factors such as lack of external rotational ROM, poor glenohumeral joint control, involvement of the biceps long head, and inadequate end-range force development. These factors by their own or together contribute to instability and a lack of control during the cocking phase.
Athletes with inside impingement typically report pain in the posterior-superior shoulder during the cocking phase and may describe sensations of "dead arm syndrome" or instability after high frequency of throwing. However, these symptoms often stem from insufficient motor control and the shoulder’s limited ability to handle the extreme forces of repetitive throwing, rather than from neurological issues or true mechanical instability.
During the late cocking phase, the posterior-superior rotator cuff (particularly the supraspinatus and the anterosuperior fibers of the infraspinatus) may be compressed between the humeral head and the labrum. This position places high loads on the biceps long head tendon insertion on the superior labrum, increasing the risk for SLAP (superior labrum anterior to posterior) lesions or biceps related pathologies, which often occurs in the tendon where it passes bicipital grove. The combined effects of rotational compression of the rotator cuff and biceps tendon tension are amplified if there is a tight posterior capsule, which can cause the undersurface of the rotator cuff to be compressed against the glenoid and humeral head.
Assessment
As mentioned, inside (or internal) impingement can arise from various underlying factors, making it essential to identify the primary contributors for each athlete. Range of motion (ROM) should be thoroughly assessed, with particular attention to external rotation (ER) ROM and internal rotational strength during the cocking phase. The athelte´s shoulder should be able to external rotate without any discomfort and there should be an end feel that is firm and slightly springy, but not a solid block. Any signs of apprehension from the athlete in this position should be noted, as this may indicate anterior instability or a lack of motor control.
To further assess the involvement of the biceps long head tendon and its attachment to the labrum, specific provocative tests can be performed. The Biceps Load II test and the Resisted Supination External Rotation test are both effective options. In these tests, the athlete actively contracts the biceps while in the cocking phase position, which can help to reveal any instability or discomfort associated with biceps tendon engagement. If the athlete shows apprehension or reluctance to contract the biceps during these tests, this may suggest anterior instability. This suspicion is strengthened if the athlete is able to fully contract the biceps without apprehension when the clinician repositions the humeral head (for example, by applying posterior pressure to the humeral head during the test).
In summary, identifying the athlete’s specific limitations, instability patterns, and responses to these tests provides valuable insight into the underlying causes of internal impingement, which can inform more targeted and effective rehabilitation strategies.
Management
Managing inside impingement effectively requires early detection and intervention to prevent progression to more serious injuries, especially in overhead athletes. The treatment approach should be tailored to the specific underlying issues identified in each case. In athletes with limited external rotation range of motion (ROM), the primary goal is to restore ROM, particularly in external rotation, as well as to strengthen the muscles responsible for end-range rotational control. Limited external rotation can contribute to increase stress and compression of the rotator cuff during the cocking phase, so improving ROM and control in this range is essential.
For athletes who have sufficient external rotation but struggle with motor control or strength, the focus should shift to enhancing both strength and control, especially in the end-range external rotation position required during the cocking phase of throwing. This phase places high demands on shoulder stability and motor control, and weakness here can lead to overuse injuries and poor performance. Exercises targeting internal rotation (IR) strength and control at end-range are critical to preventing symptoms and ensuring efficient mechanics. Here, one can kill two birds with one stone by performing heavy resistance IR training in the cocking position, which will likely increase both external rotation (ER) range of motion and IR strength.
When a confirmed SLAP (superior labrum anterior to posterior) lesion is present, a more cautious, structured protocol is required. SLAP lesions involve damage to the superior labrum where the long head of the biceps tendon attaches, and improper loading can compromise healing. To protect the biceps tendon during the early stages of recovery, a good rule of thumb is to avoid progressive loading of the biceps tendon until the athlete has restored active ROM and can perform pain-free isometric exercises. The proximal aspect of the long head of the biceps tendon is tightly positioned over the humeral head, especially when the arm is by the side or extended, which increases the risk of compressive forces. During the initial rehabilitation phase, the safest way to load the biceps tendon is with the shoulder positioned at 90 degrees of abduction in the scapular plane, with the arm supported to minimize compressive load on the tendon.
In cases where surgical intervention is needed for SLAP lesions, post-operative rehabilitation differs depending on the surgical technique used. In general, the acute recovery and early rehabilitation phases are extended compared to non-surgical management. The total duration of rehabilitation after SLAP surgery varies based on factors such as the type of sport and the level of overhead activity required. Athletes can typically expect a minimum of one year of rehabilitation before returning to play, though full functional restoration may take longer for some, particularly those in high-demand throwing sports. It is also important to note that definitions of "return to sport" and "success" vary across studies, making these numbers a general guide rather than absolute expectations.
Summary
Inside, or internal, impingement is a common cause of posterior-superior shoulder pain in overhead athletes, arising from compression of the rotator cuff against the back of the glenoid during the cocking phase. This condition often results from factors like limited external rotation ROM, poor joint control, and biceps involvement, which collectively contribute to shoulder instability. Effective management requires early identification of the primary contributing factors, thorough assessment of ROM and control, and tailored interventions. For those with SLAP lesions, a cautious, structured approach is essential to ensure proper healing and minimize re-injury risks, ultimately supporting a safe return to sport.
In the next part of this series, we’ll turn our attention to shoulder instability, a condition that can result from repetitive stress, trauma, or poor biomechanics. Shoulder instability can lead to pain, weakness, and an increased risk of dislocations, affecting both athletic performance and daily function. We’ll dive into the causes, assessment methods, and treatment strategies for managing shoulder instability in overhead athletes.
