Preventing Shoulder Impingement by Chris Gellert, PT, MMusc & Sportsphysio, MPT, CSCS, AMS

 Introduction The shoulder is a complex joint involved in daily activities such as getting dressed, reaching into a cupboard and sport activities such as baseball and swimming. Because the shoulder is truly a ball and socket joint, it moves freely in six different motions, making it more susceptible to injury. In this article, we will review the anatomy and biomechanics of shoulder movement, clinical presentation, management and physical therapy for treating shoulder impingement syndrome, and training strategies to work with clients with previous shoulder impingement. Shoulder anatomy and biomechanics Anatomy Let’s look at the shoulder anatomically There are four major joints within the shoulder complex, which include the glenohumeral joint, acromioclavicular joint, sternoclavicular joint and scapulothoracic joint.

Figure 1. Joints within the shoulder complex Muscles The four primary muscles that make up the rotator complex includes the supraspinatus, infraspinatus, teres minor and subscapularis. These four muscles provided stability and are involved in multiple daily activities, such as reaching, lifting, getting dressed and throwing a ball. Per the research, the supraspinatus muscle is the weakest of the four rotator cuff muscles, is poorly vascularized and is the most often surgically repaired.

Supraspinatus muscle Infraspinatus muscle Teres minor muscle Subcapularis muscle Side raises the arm Externally rotates the arm Externally rotates the arm Internally rotates the arm Figure 2. Rotator cuff muscles

Biomechanics During normal shoulder elevation(flexion) and abduction(side raising)movement, the scapula in red, upwardly rotates on the thorax. This is seen in figure 3. This is called the scapulohumeral rhythm(SHR). Biomechanically, there is 120 degrees of movement that occurs at the glenohumeral joint and 60 degrees at the scapulothoracic joint. SHR is defined as the movement relationship between the humerus and the scapula during arm raising movements. Arthokinematics is defined as the movement that occurs between two joint surfaces as seen in figure 4. As seen in figure 4, during abduction of the shoulder, the humerus slides down in the glenoid cavity(vertical arrow). With continued side raising as seen in figure 3, the scapula upwardly rotates on the thorax.

Figure 3. Normal upward rotation of Figure 4. Arthokinematics of shoulder scapula on thorax Abnormal scapulohumeral rhythm • As seen in figure 5, this patient is demonstrating shoulder “hiking.” This is caused by a rotator cuff tear where the individual does not have the musculotendinous connection/strength to abduct the arm, is limited due to joint and capsule hypomobility (restriction) known as adhesive capsulitis(frozen shoulder), or has pain and/or muscular weakness preventing the ability to raise the arm to the side.  

 Figure 5. Abnormal scapulohumeral rthym

Clinical presentation Someone suffering from shoulder impingement syndrome, will complain of pain along the front to side of the shoulder at rest and possibly complain of pain or difficulty sleeping on the affected side. They will often complain of pain with active shoulder side raising as seen in figure 6. Observing their posture, they will be present with bilateral rounded shoulders in an internally rotated position.

  Figure 6. Shoulder impingement(Painful arc) Contributing risk factors Potential risk factors include overtraining the front part of the body(ie. pectorals, anterior deltoid, and bicep muscles), poor posture, tight posterior capsule, and repetitive unilateral lifting to the side are all factors. Medical and Physical Therapy Treatment Patients are taught to rest their shoulder and may be advised by their physician to take non-steroidal for inflammation and pain. X-rays typically reveal no significant findings. Physical therapy is effective in improving soft tissue mobility in tight pectoral major, pectoral minor and subscapularis muscles. Patients are educated on how to stretching their posterior capsule. Stretching the posterior capsule, enables the humerus to glide within the glenohumeral cavity(as seen in figure 4). Physical therapists teach patients to stretch tight chest muscles, posterior capsule(Kuhn, J., 2009) and upper trapezius muscles. Strengthening focuses on targeting the weaker upper posterior musculature that includes rhomboids, low trapezius, external rotator cuff muscles, serratus anterior statically. Then patient is taught scapular stabilization and dynamic strengthening exercises. Impingement syndrome Shoulder impingement may be either classified as primary or secondary. Evidenced based research has shown that shoulder impingement is a common condition believed to contribute to the development or progression of rotator cuff disease(Paula M. Ludewig, 2011) 1. Primary(Mechanical) impingement: Is caused by a mechanical dysfunction such as bursa, AC joint, acromion, humerus or rotator cuff/supraspinatus tendon beneath the coracromial arch. This is a mechanical problem that may result from sub acromial crowding.

2. Secondary(Structural) impingement: Is caused by a relative decrease in sub acromial space caused by instability of the glenohumeral joint, tight posterior capsule and weakness of scapulothoracic musculature.

• Decrease in sub acromial space comprises the supraspinatus tendon, predisposing it to micro tears leading to degeneration and ultimately tearing.

• Tightness of the posterior capsule causes the humerus to migrate anterosuperior into the AC joint.

• Weakness of scapulothoracic muscles leads to abnormal positioning of the scapula. This affects the scapulohumeral rhythm(defined as the movement relationship between the humerus and the scapula during arm raising movements). With this disruption, the acromion is not elevated properly to allow unrestricted passage of the rotator cuff under the coracromial arch.

Recommendations for training/specific exercises with rationale To help a client with a history of shoulder impingement, the emphasis is to create scapular stability and balance between shoulder muscles dynamically. Continuation of posterior capsule stretching as seen in figure 7.

Scaption strengthening: lateral raise-arms abducted with 30 degree anterior to the frontal plane.

• Scapular protraction-(strengthening serratus anterior and low trapezius biomechanically, together cause an upward rotation of the scapula to maintain the sub acromial space above 90 degrees of shoulder elevation.

Figure 8. “Serratus Punch” Figure 9. Low trapezius exercise anterior supine pulldown exercise

• Scapular retraction strengthening-performing mid row exercise (decreases load to front of the shoulder), low trapezius exercise and lat pull-down.

• External rotation strengthening-ideal is side lying, which is more isolative for teres minor, and infraspinatus recruitment(decreases the load to the anterior shoulder).

Exercises AVOIDED with impingement syndrome The following exercises should be avoided based on science and biomechanics.

• Behind the neck press exercise-exercise requires the shoulder to start in a lateral and abducted position. The second component involves pulling the shoulder into retracted positioning(pinching the shoulder blades together), while maintaining an externally rotated position. This maneuver tends to lead to increases impingement, where the rotator cuff becomes compromised under the acromion irritating the tendon and causing it to become inflamed.

• Shoulder press exercise-creates direct axial loading to the acromioclavicular joint, underlying supraspinatus and the sub deltoid bursa.

• Supine dumbbell pullover exercise-forces the rotator cuff tendons and bursa against the undersurface of the acromion when the arms are hyper flexed.

• Upright row exercise-during this exercises the arm is maintained in an internally rotated position throughout the entire range of motion.

Research Various studies have evaluated if a specific exercise strategy, targeting the rotator cuff and scapula stabilizers, improves shoulder function and pain more than unspecific exercises in patients with sub acromial impingement syndrome. Holmgren., T., (2012) performed a study that examined 102 patients with chronic(over six months) persistent sub acromial impingement syndrome, whom earlier conservative treatment had failed. Results: She discovered the group that performed eccentric exercises for the rotator cuff and eccentric/concentric exercises for scapular stabilizers, had significantly reduced pain, improved function, whereby reducing the risk for arthoscopic decompression surgery. Conclusion: Focusing on strengthening eccentric exercises for the rotator cuff and concentric/eccentric exercises for the scapula stabilizers, is effective in reducing pain and

improving shoulder function in patients with persistent sub acromial impingement syndrome. Bernhardson, S., (2012) also wanted to examine which exercise were the most effective for sub acromial impingement syndrome. Conclusion: A 12-week eccentric strengthening program targeting the rotator cuff and incorporating scapular control and correct movement pattern can be effective in decreasing pain and increasing function in patients with sub acromial impingement syndrome. Summary The shoulder is a complex unit that is comprised of a multitude of ligaments, tendons, connective tissue, muscles that synergistically initiate and correct movement, and stabilize when an unstable environment. Understanding the anatomy, biomechanics and weak links of the shoulder, common injuries and evidenced based training strategies, should provide you with the insight to better understand and work with clients who have shoulder impingement in designing effective programs that yield outstanding results for your clients. Chris is the CEO of Pinnacle Training & Consulting Systems(PTCS). A continuing education company, that provides educational material in the forms of home study courses, live seminars, DVDs, webinars, articles and min books teaching in-depth, the foundation science, functional assessments and practical application behind Human Movement, that is evidenced based. Chris is both a dynamic physical therapist with 15 years experience, and a personal trainer with 19 years experience, with advanced training, has created over 10 courses, is an experienced international fitness presenter, writes for various websites and international publications, consults and teaches seminars on human movement. For more information, please visit www.pinnacle-tcs.com

REFERENCES Bernhardsson, B., et al (2012), ‘Evaluation of an exercise concept focusing on eccentric strength training of the rotator cuff for patients with sub acromial impingement syndrome, Clinical Rehabilitation, pp. 1-9.

Holmgren, T., 2012, ‘Effect of specific exercise strategy on need for surgery in patients with sub acromial impingement syndrome: randomized controlled study,’ British Journal of Medicine, pg. 344.

Kuhn, J., 2009, ‘Exercise in the treatment of rotator cuff impingement: A systematic review and a synthesized evidence-based rehabilitation protocol,’ Journal of Shoulder Elbow Surgery, vol. 18, pp. 38-160.

Ludewig,P., 2011, ‘Shoulder Impingement: Biomechanical Considerations in Rehabilitation,’ Journal of Manual Therapy, vol. 16, issue , pp. 33–39.

Sein, M., et al., 2010, ‘Shoulder pain in elite swimmers: primarily due to swim-volume- induced supraspinatus tendinopathy,’ British Journal of Sports Medicine, vol. 44, pp.105-113 Smith, M., et al., 2009, ‘Upper and lower trapezius muscle activity in subjects with sub acromial impingement symptoms: Is there imbalance and can taping change,’ Physical Therapy in Sport, pp. 1-6.