Shoulder Impingement: The What, Why and How

It is a well-documented fact since the mid-1990s that shoulder pain is the second most common musculoskeletal complaint in physiotherapy clinics after low back pain1,2. Commonly, patients would complain of pain over the lateral aspect of the shoulder (over the deltoid tubercle) and/or have difficulty lifting their arm up. The common diagnosis would normally be either a frozen shoulder or shoulder impingement. But what causes the pain? Primary causes of shoulder pain have been difficult to pin down due to the complexity of the shoulder3.  

A common source of shoulder pain is impingement of the structures under the sub-acromial arch, leading to the diagnosis of shoulder impingement. The commonly accepted causes of shoulder impingement are generally tendinitis or bursitis2. However, the question we therapists always ask is what had caused the tendonitis or bursitis? 

Causes of Shoulder Impingement

There are 2 broad categories of causes of impingement, internal and external impingement, with external impingement being further sub-divided into primary and secondary causes. This flow chart below summarizes the classification3:

The most common shoulder impingement cases presented to a physiotherapy clinic is the external secondary impingement cases. However, on the assessment of clients with a shoulder impingement, the most common problem we see is the weak scapular stabilizers leading to poor scapular humeral control. This weakness can also be attributed to a forward head posture with protracted shoulders. With the shoulders being in a protracted position, the scapular stabilizers would be placed in a lengthened position, altering the length-tension relationship, leading to weakness and poor control. Shoulder protraction also decreases the sub-acromial space as the scapular is rotated anteriorly. Tightness in the posterior capsule of the shoulder has also been closely associated with shoulder impingement as it pushes the humeral head against the sub-acromial arch on flexion, entrapping the structures within the sub-acromial space3,4.  

How to manage Shoulder Impingement

Conventional physiotherapy management, through the years, has been described as range of motion (ROM) exercises, soft tissue mobilization and modalities like heat pack, therapeutic ultrasound, lasers and SWD (short wave diathermy)5,6. However, these generally are just symptomatic relief. The ROM exercises would help maintain the shoulder range and prevent adhesive capsulitis (frozen shoulder). As for the soft tissue mobilization, it would help loosen up any tight muscles of the shoulder region arising from the compensatory mechanisms that the client adopts to decrease their pain. The modalities would help reduce the inflammation of the tendon or bursa. However, none of these treatments would be actually correcting the impaired mechanics of the shoulder.

However, in the past decade, more studies have started to cover manual therapy and therapeutic exercise protocols; comparing them against the conventional physiotherapy management5,6. Manual therapy has been defined as manually applied mobilization techniques that would directly affect the joint movement. These techniques are normally directed into the direction of stiffness or resistance to improve the flexibility or mobility of tight structures like ligaments or muscles at the position of pain. Therapeutic exercises are those taught to patients to improve the strength and/or neuromuscular control of the shoulder joint, thus decreasing the clients’ pain.

Therapeutic Exercises

Scapular stabilization exercises have been the choice in recent research as they have been found to bring about the best therapeutic results in shoulder impingement and are simple to do. Below are simple scapular stabilizing exercises that are taught to patients:

  1. Scapular Retraction (Figure 1)
    Pull your scapular backwards and downwards. This activates your rhomboids, serratus muscles and lower traps to stabilize the scapular in the sagittal plane.
  2. Scapular Clock (Figure 2)
    With the palm against the wall at an 8 o’clock position, and the shoulder starting at 45o flexion, move the shoulder into the various clock positions, e.g. 3 o’clock, 6 o’clock, etc. The palm position can be progressed to move towards a 4 o’clock position while moving the shoulder. This facilitates the scapular into elevation, depression, retraction while the humeral bone moves independently from the scapular.
  3. Low Row (Figure 3)
    Pushing one’s arm backwards while pulling the scapular downwards activates the lower traps, an essential muscle in improving the scapular control as the arm is raised or lowered.

Scapular stabilization exercises should be progressed into functional activities to manage the impingement and close monitoring of the scapular-humeral rhythm is essential while progressing into functional activities.

Figure 1: Scapular Retraction
Figure 2: Scapular Clock
Figure 3: Low Row

Conclusion

In managing shoulder impingement, one should not neglect to look into the stability of the scapular as it plays a very important role in the biomechanics of the movement of the shoulder. Ample attention should be given to improving the stability and control of the scapular muscles to give patients the relief they need from shoulder pain.

References

  1. van der Windt DA, Koes BW, de Jong BA, et al. Shoulder disorders in general practice: incidence, patient characteristics, and management. Ann Rheum Dis. 1995;54:959–964.
  2. Bang MD, Deyle GD. Comparison of supervised exercise with and without manual physical therapy for patients with shoulder impingement syndrome. J Orthop Sports Phys Ther. 2000;30:126–137.
  3. Brukner P and Khan K. Shoulder Pain Clinical Sports Medicine 3rd Edition, 2007: 243-288
  4. Shankwiler JA, Burkhead WZ. Diagnosis, evaluation and conservative management of impingement syndrome. Operative Techniques in Sports Medicine, 1994: 2(2): 89-97
  5. Conroy DE, Hayes KW. The effect of joint mobilization as a component of comprehensive treatment of primary shoulder impingement syndrome. J Orthop Sports Phys Ther. 1998;28:3–14.
  6. Winters JC, Sobel JS, Groenier KH, et al. Comparison of physiotherapy, manipulation, and corticosteroid injection for treating shoulder complaints in general practice: randomised, single blind study. BMJ. 1997;314:1320–1325.

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