Internal shoulder impingement | Diagnosis & Treatment

Internal impingement of the shoulder is a term used to describe a group of symptoms that occur when the soft tissues of the rotator cuff and joint capsule in the shoulder get pinched or compressed between the glenoid (part of the shoulder blade) and the humerus (upper arm bone). This usually happens when the shoulder is in a certain position, such as when it is abducted (moved away from the body) and externally rotated (turned outward). It is different from external impingement, where the cuff and bursa get pinched on the structures of the coracoacromial arch. The exact cause of internal impingement is still debated, but it seems to be a normal occurrence in certain shoulder positions. Imaging findings in internal impingement may include partial-thickness cuff tears, labral pathology, and bone changes.

There are two types of internal impingement syndromes that have been recognized: posterosuperior impingement and anterosuperior (anterior) impingement. Posterosuperior internal impingement occurs when the posterosuperior rotator cuff, close to the junction of the supra and infraspinatus tendons, comes into contact with the posterosuperior glenoid. Anterosuperior impingement, on the other hand, involves impingement between the anterior rotator cuff and the anterosuperior glenoid. These conditions are characterized by the impingement of the soft tissues of the rotator cuff and joint capsule on the glenoid or between the glenoid and the humerus.

Epidemiology

The incidence of symptomatic internal impingement is unknown due to the variety of associated pathologic lesions, diagnostic difficulty, and incomplete reporting of the condition. However, it is commonly observed in younger patients, typically those under 40 years old, who participate in activities requiring repetitive external rotation and abduction. While throwing activities, such as baseball, are classically associated with symptomatic internal impingement, it is important to note that the condition can occur in athletes and non-athletes alike. Although non-athletes may also develop the condition, the majority of those with symptomatic internal impingement are throwing athletes.

Clinical Picture & Examination

Internal impingement of the shoulder can present with various signs and symptoms. Patients with symptomatic internal impingement often experience chronic, diffuse posterior shoulder pain. This pain is typically worsened by activities that require abduction and external rotation of the shoulder. In throwing athletes, there may also be a gradual decrease in throwing velocity, accuracy, and overall performance over a period of months. It is important to note that non-athletes may report acute posterior shoulder pain rather than chronic pain.

Patients with internal impingement may also complain of shoulder stiffness or the need for a prolonged warm-up. They may describe a decline in performance, including loss of control or decreases in pitch velocity. Posterior shoulder pain, especially during the late cocking phase of the throwing cycle, is a common complaint.

Examination

During physical examination, there may be posterior glenohumeral joint line tenderness. There is often increased external rotation and decreased internal rotation of the shoulder, described as GIRD. Symptoms of instability, such as clicking and subluxation, may also be present, although the coexistence of both anterior instability and symptomatic internal impingement is less common than previously thought. In the following video, we show you how to assess for a GIRD = glenohumeral internal rotation deficit:

It is important to rule out other conditions, such as rotator cuff disease, as symptomatic internal impingement can be a common cause of rotator cuff lesions in young overhead athletes. A thorough history and physical examination, including palpation of the glenohumeral joint and assessment of range of motion, should be performed to properly diagnose internal impingement.

There are several orthopedic tests that can be helpful in diagnosing internal impingement of the shoulder. These tests can aid in identifying specific signs and symptoms associated with this condition. However, it is important to note that the diagnostic accuracy of these tests may vary, and further research is needed to establish their clinical value.
A test that was described by Meister et al. (2004) is the posterior impingement sign. According to the authors, this test has a sensitivity of 75.5% and a specificity of 85% in the diagnosis of internal shoulder impingement in overhead athletes with posterior shoulder pain. When only athletes with noncontact injuries (gradual onset of pain) were considered, sensitivity was 95% and specificity was 100%. In the following video, we will show you how to perform this test:

Additionally, imaging studies such as magnetic resonance imaging (MRI) and arthrography can provide valuable information for diagnosing internal impingement. These imaging modalities can help identify specific findings associated with internal impingement, such as Bennett lesions (exostosis of posteroinferior glenoid rim), sclerosis of the greater tuberosity, posterior humeral head cysts, rounding of the posterior glenoid rim, and posterosuperior labral tears.

It is important to note that the diagnostic accuracy of these tests may vary, and they should be used in conjunction with a thorough history, physical examination, and imaging studies to make an accurate diagnosis of internal impingement.

Treatment

Non-operative management focuses on rest and stretching protocols, particularly targeting the posterior capsule of the shoulder. Intense non-operative management may include activity modification, rest from overhead throwing, and anti-inflammatory medications.
For internal impingement of the shoulder, rehabilitation exercises play a crucial role in the treatment process. According to Cools et al. (2007) the rehabilitation consists of 3 main pillars:

Rehabilitation of acquired instability of the glenohumeral joint

The main goals of treatment for acquired shoulder instability are to restore stability, improve function, and reduce symptoms. The specific goals may vary depending on the individual’s condition and the severity of the instability. However, in general, the following goals are commonly pursued in the treatment of acquired shoulder instability:

• Restore Muscular Balance: Treatment aims to restore the balance between the muscles around the shoulder joint, particularly the rotator cuff and scapular stabilizers. Strengthening these muscles helps provide dynamic stability to the shoulder and improve its overall function.
• Improve Proprioception and Neuromuscular Control: Proprioception refers to the body’s ability to sense the position and movement of its parts. Enhancing proprioception and neuromuscular control of the shoulder joint is important in preventing further instability episodes and improving overall joint stability.
• Enhance Range of Motion: Treatment may involve exercises and techniques to improve the range of motion of the shoulder joint, particularly addressing any limitations in internal rotation range of motion that may contribute to internal impingement.
• Reduce Pain and Inflammation: Pain and inflammation associated with acquired shoulder instability are often addressed through various modalities, such as ice therapy, anti-inflammatory medications, and activity modification.
• Gradual Return to Activity: Rehabilitation aims to gradually reintroduce the individual to their desired activities, such as sports or physical activities, while ensuring that the shoulder is adequately stabilized and protected.

Rehabilitation of GIRD

• Sleeper Stretch: The sleeper stretch is a popular exercise for addressing internal impingement. It focuses on stretching the posterior capsule of the shoulder. To perform this exercise, lie on your side with the affected shoulder on the bottom. Bend your elbow to 90 degrees and use your opposite hand to gently push your forearm down towards the bed or floor. Hold the stretch for about 30 seconds and repeat several times.
• The cross-body stretch is an exercise commonly recommended to address Glenohumeral Internal Rotation Deficit (GIRD). It is an angular stretching technique that involves horizontal adduction of the arm. During the cross-body stretch, the arm is moved across the body into horizontal adduction. This stretch helps to target the internal rotators of the shoulder and can help improve the range of motion in the glenohumeral joint.It is important to perform both stretches with caution and pay attention to the patient’s reaction. A stretching feeling at the back of the shoulder is allowed, but if the patient feels pain anteriorly (in the front of the shoulder), the intensity of the stretching should be reduced.

Rehabilitation of Scapular Dyskinesis

To treat scapular dyskinesis, several exercises are commonly recommended. These exercises aim to improve the strength, stability, and coordination of the muscles that control scapular movement. Here are some exercises that are often included in a comprehensive treatment plan for scapular dyskinesis:

• Scapular Retraction: This exercise focuses on strengthening the muscles that retract the scapula, such as the middle and lower trapezius. It can be performed by standing or sitting upright and squeezing the shoulder blades together, holding for a few seconds, and then releasing. This exercise helps improve scapular stability and promotes proper alignment.
• Scapular Squeeze: Similar to scapular retraction, the scapular squeeze exercise targets the muscles that retract the scapula. It involves squeezing a small ball or towel between the shoulder blades while maintaining good posture. This exercise helps activate the muscles responsible for scapular stability and control.
• Wall Slides: Wall slides are effective for improving scapular upward rotation and strengthening the serratus anterior muscle. Stand with your back against a wall, elbows bent at 90 degrees, and palms facing forward. Slowly slide your arms up the wall while keeping your shoulder blades down and back. Return to the starting position and repeat. This exercise helps promote proper scapular movement and muscle activation.
• Prone Y-T-W-L Exercises: These exercises target the muscles of the upper back, including the trapezius and rhomboids. Lie face down on a mat or bench with your arms in different positions to form the letters Y, T, W, and L. Lift your arms off the ground while squeezing your shoulder blades together and hold for a few seconds before lowering. These exercises help strengthen the muscles involved in scapular stabilization and improve posture.

References

Cools, A. M., Declercq, G., Cagnie, B., Cambier, D., & Witvrouw, E. (2008). Internal impingement in the tennis player: rehabilitation guidelines. British journal of sports medicine, 42(3), 165-171.

Corpus, K. T., Camp, C. L., Dines, D. M., Altchek, D. W., & Dines, J. S. (2016). Evaluation and treatment of internal impingement of the shoulder in overhead athletes. World Journal of Orthopedics, 7(12), 776.

Leschinger, T., Wallraff, C., Müller, D., Hackenbroch, M., Bovenschulte, H., & Siewe, J. (2017). Internal impingement of the shoulder: a risk of false positive test outcomes in external impingement tests?. BioMed Research International, 2017.

Meister, K., Buckley, B., & Batts, J. (2004). The posterior impingement sign: diagnosis of rotator cuff and posterior labral tears secondary to internal impingement in overhand athletes. American journal of orthopedics (Belle Mead, NJ), 33(8), 412-415.

Spiegl, U. J., Warth, R. J., & Millett, P. J. (2014). Symptomatic internal impingement of the shoulder in overhead athletes. Sports medicine and arthroscopy review, 22(2), 120-129.