Shoulder Impingement: Looking Beyond the Shoulder

Let’s start with a simple case study:

Liz is an 18yo female who comes into the clinic with a complaint of anterior shoulder pain. Liz is training for her college volleyball season and has had on and off shoulder pain all throughout high school, but now that she has a scholarship for college and she really wants to be able to keep her scholarship and prevent her shoulder from getting worse.

What are the key points we can take away:

  • Anterior shoulder pain: this gives us a starting point. We are going to want to probe for more information (nerve symptoms, radiating pain, certain positional factors that make it worse/better, description of the pain etc.)

  • On & off pain: indicates that this may be a chronic issue -osis vs. -itis if we are looking at some sort of tendinopathy. This will also be important with treatment and pain management strategies

  • Volleyball player: overhead athlete, lots of impact through her shoulder and back.
    We are going to want to look at her arm but also assess her back/posture
    and LE’s depending on how it may impact her overhead mobility.

As I assess and get more answers, I notice her posture is relatively good- if anything she has more of the posture of a dancer- increased lumbar lordosis, mild swayback. As I probe for more information about her pain I find that her pain is primarily triggered with serving and blocking, the pain doesn’t persistent, and she denies any other symptoms besides the sharp pain in her anterior shoulder (she points directly to the acromion and slightly below into her biceps). Her strength assessment comes back pretty unremarkable. She does demonstrate some scapular winging greater on her impacted side and some scapular tipping (an indication of scapular instability) with shoulder flexion and abduction.
Special tests that came back positive:

  • (+) Hawkins Kennedy

  • (+) Neers

These two tests indicate impingement. So what is impingement?



The shoulder is composed of a couple of different articulating surfaces. First off, the thoracic cage from which extends clavicle via the sternum. The clavicle articulates with the scapula. The scapula is a primarily flat bone on the posterior aspect of your shoulder except for the lateral superior concave portion (the glenoid cavity) that articulates with the humerus via the humeral head. These 3 bones comprise the glenohumeral joint (aka shoulder joint). This type of joint is considered a ball and socket joint. You have the ball which is the humeral head that articulates with the small cup or glenoid cavity. The movement of this ball is limited by a couple of different structures:

  • Ligaments

  • Glenoid labrum

  • Joint Capsule

  • Rotator Cuff

  • Acromion

The ligaments provide passive joint stability by attaching along the glenoid rim to the humeral head, these are composed of the following

  • Anterior superior glenohumeral ligament

  • Middle glenohumeral ligament

  • Inferior glenohumeral ligament (anterior band)

  • Inferior glenohumeral ligament (posterior band)

These ligaments partly fuse with the joint capsule and the glenoid labrum. Hypermobility of the humeral head may either indicate loose ligaments (more common in young females) and passive instability or in some cases tears (with or without pain depending on the acuity of the injury). The glenoid labrum acts as a wedge along the edge of the glenoid cavity. Similar to how a tire wedge acts, it prevents the humeral head from rolling off the edge of the glenoid cavity. The capsule encompasses the entire joint and acts to maintain the joint lubrication in place but also provides an essential job of maintaining negative joint pressure. Negative joint pressure is essentially a vacuum holding the joint in place but also reducing friction within the joint. Weakness and instability due to and
the impaired rotator cuff can causes changes in the negative space (1). This can contribute to an increased risk of arthritis and joint degeneration. The rotator cuff is comprised of 4 muscles

  1. Supraspinatus

  2. Infraspinatus

  3. Teres minor

  4. Subscapularis

These muscles provide active stability to the shoulder in conjunction with actions and movements to the shoulder joint. However, due to limited space between the acromion and the humeral head, the supraspinatus can easily be inhibited leading to increased instability and limited overhead shoulder motion. In a normal shoulder, the subacromial space is between 1.0-1.5 centimeters(2). With poor posture and tight upper traps, leading to scapular elevation and rotation, this space can be significantly reduced leading to pain, inflammation, and eventual tears to the supraspinatus. In the case of this young athlete, multiple factors are coming into play. Here are some of the contributing factors

  • Repetitive overhead movements

  • High impact through the shoulder

  • Swayback posture

  • Impaired scapular motor control

  • Impaired thoraco/plevic mechanics

I can’t change the way volleyball is played, however, I can reinforce the importance of cross-training and limiting the amount of time she is hitting overhead outside of games. It is easy to narrow the focus to purely the shoulder, but even in volleyball the trunk/pelvis and lower extremities (LE) play a key roll in all the motions. Focusing on LE strength, thoracic flexibility, and rotation can immensely reduce the amount of force through the shoulder joint. Exercises that focus on trunk rotation, trunk extension, pelvic rotation, and pelvic loading, as well as pectoral stretches and strengthening can significantly increase the longevity of an overhead athlete and reduce the incidence of injury.

Her swayback posture, another contributing factor to her shoulder injury, additionally places her at a higher risk of a back injury. Her upper shoulder girdle is naturally behind her pelvis when it should be stacked above her pelvis. When she goes up to hit the ball her shoulder girdle falls even further behind the ball leading to increased instability due to poor abdominal stabilization mechanics. This brings up the concept of muscle length-tension. When a muscle is either severely shortened or extremely the muscle loses its strength. When biomechanically placed in this lengthened position the lengthened muscles lose strength and stability and thus increase the risk of injury as well as muscle tears. In volleyball serves/spikes/blocks these lengthened muscles are her abdominal muscles but also her hip flexors. The abdominal muscles and hip muscles not only are major power generators but also key stabilizers. By arching her back she reduces the forces of those muscles and thus has to compensate with her shoulder muscles-which are not intended to sustain such major forces. When fixing posture, it is important that this becomes a habit. Addressing behavioral components and maintaining the posture throughout the day is essential.



 Impaired scapular motor control is similar to suddenly walking on a very wobbly bridge or boat. Excellent balance reactions and compensatory strategies are essential to preventing a fall and injuries. A strong platform or base allows free movement and the ability to walk unencumbered. Scapular stability is the foundation in order to prevent injury and allow the shoulder to move around freely. Most athletes that I have worked with have overall excellent strength, however, their motor control is lacking. Certain athletes have a very good rapport with their bodies and can easily correct a weakness and motor impairment, but not all. The key is starting with simple exercises, no resistance, and starting with an isometric contraction (ie holding the position in one place). As the control gets better ie no more scapular winging, good scapular retraction, and depression a progressing to closed chain exercises and then open-chain exercises can occur.  Leading finally to overhead motions. Again the key to success is being able to maintain the proper positioning throughout the day. In order to prevent injury, you have to keep the scapula in a good position throughout the day-not just when you are hitting the ball or reaching overhead. 

Finally, restricted motion in the thoracic spine and pelvis can lead to increased torque and rotation going through the shoulder. Not only does improving spine mobility and the pivot motion of the hips prevent shoulder injury but this is an amazing way to increase power in serves and spikes. Exercises that facilitate trunk and pelvic openers are fantastic and then incorporating strength exercise within that new movement. The key to success again is to gain strength in the increased range of motion as well as maintain abdominal stabilization! Protect the spine with good abdominal and especially transverse abdominal stabilization. Through these exercises, good posture MUST be maintained. Many times I have had clients ask me why I am focusing on abdominal exercises or leg exercises when their pain is in their shoulders. It’s essential for them to understand the connection between
legs/spine/shoulder. My classic example is to pinch the client’s shirt at their hip, all of a sudden the tension in the shoulder portion of their shirt builds up. It’s a very simplistic explanation but it can clearly get the image across. If the focus is on the shoulder, many times the root of the problem is missed and only a small portion of the problem is addressed.

To healthy shoulders and healthy bodies! Keep moving and stay healthy.

References

  1. Hurschler C, Wulker N, Mendila M. The effect of negative intraarticular pressure and rotator cuff force on glenohumeral translation during simulated active elevation. Clin Biomech. 2000; Jun; 15(5): 306-14.

  2. Umer M, Qadir I, Azam M. Subacromial impingement syndrome. Orthop Rev. 2012; May; 4(2):
    e18.

Images

  1. Glenohumeral Joint. Original image from: https://www.kenhub.com/en/library/anatomy/the-shoulder-joint

  2. Types of Standing Posture. Original image from https://www.thebackclinic.net.au/how-to-correct-sway-back-posture.html.