Rotator cuff related shoulder pain: “Subacromial impingement”

Subacromial impingement syndrome.

It’s quite a mouthful and a diagnosis that will make you fearful of ever using your shoulder and arm again. But what is it and what does it mean? Subacromial impingement is considered to be the most common musculoskeletal condition affecting the shoulder and is estimated to affect at least one in four people at some point in their lifetime. It is based upon the idea of tissues within the shoulder joint undergoing compression during certain functional movements, especially ones that involve the arm being raised above shoulder height.

In essence this theory suggests that one of the muscles that contributes to the rotator cuff (supraspinatus) gets pinched underneath the bony roof of your shoulder blade (acromion process) resulting in pain and inflammation of the tendon and its surrounding tissues such as the bursa (a sac of fluid that protects the tendon from abrasion). But is this really the cause of your shoulder pain? After all, up until this point in your life you’ve never had an issue with this bone or this tendon so what’s changed?

To answer this, we first must understand what tendons are and how they operate.

Tendons are the connective tissues that help connect a muscle to a bone. It is made up of collagen fibres which are closely packed to give a tendon the strength it needs to transmit the forces produced by our muscles into the bones they attach to. In fact, tendons are so robust that gram for gram these tightly packed fibres are stronger than steel!

If that’s the case, then you may be wondering how do they get damaged? Well, there are several lifestyle factors that contribute to tendon health and regeneration. Avoiding modifiable factors such as smoking, obesity, high intakes of fatty or processed foods and high cholesterol levels all contribute to maintaining healthy tendons. However, by far the most notable risk factor for tendon injury is SUDDEN CHANGES IN ACTIVTY LEVELS! Tendons do not like a sudden change in activity. If they go through a period of unaccustomed loading, especially above shoulder height, they will end up getting irritated and unhappy.

When we work a tendon to fatigue (which happens quite easily when we first start moving after a period of inactivity) it induces swelling within that tendon. This is especially true in the case of the supraspinatus tendon, which is the main tissue implicated in this diagnosis. As a result of this fatigue and swelling there is a decrease in activation of the supraspinatus muscle which plays an important roll in stabilising the shoulder joint and preventing the unwanted rise of the humeral head (top of the arm bone). Therefore, the issue is not actually subacromial impingement but rather tilting more towards an irritation of the tendon due to overuse, also referred to as overuse tendinopathy or as rotator cuff related shoulder pain.

So, what can you expect from physiotherapy management?

Physiotherapy management for rotator cuff related shoulder pain often follows a general pattern: a period of active rehabilitation, followed by a phase of self-management or independent exercise, before a gradual return to normal activity. Timelines vary significantly between individuals, and your physiotherapist will guide you on what to expect based on your specific presentation. Physiotherapy management may often include some manual therapy techniques in addition to a targeted home exercise program or work-related activity program. It is important to note that some of the exercises you will be asked to complete may bring on some discomfort or result in you working through pain. This is common, and discomfort should generally be tolerable, easing shortly after the exercise.

The reality of the situation is that this theory of shoulder impingement is now considered outdated. The evidence now shows us that decompression surgery, which was and still is the surgical procedure for this injury to date, does not outperform either placebo surgery or physiotherapy treatment in the short-, medium- or long-term outcomes. So, it's worth asking your treating team whether surgery is necessary, given the evidence that outcomes with physiotherapy treatment are often comparable over 6 to 12 months.

References

Cuff, A., & Littlewood, C. (2018). Subacromial impingement syndrome – What does this mean to and for the patient? A qualitative study. Musculoskeletal Science And Practice, 33, 24-28. doi: 10.1016/j.msksp.2017.10.008

Lewis, J. (2009). Rotator cuff tendinopathy/subacromial impingement syndrome: is it time for a new method of assessment?. British Journal Of Sports Medicine, 43(4), 259-264. doi: 10.1136/bjsm.2008.052183

Lewis, J. (2011). Subacromial impingement syndrome: a musculoskeletal condition or a clinical illusion?. Physical Therapy Reviews, 16(5), 388-398. doi: 10.1179/1743288x11y.0000000027

Lewis, J. (2016). Rotator cuff related shoulder pain: Assessment, management and uncertainties. Manual Therapy, 23, 57-68. doi: 10.1016/j.math.2016.03.009

Lewis, J., McCreesh, K., Roy, J., & Ginn, K. (2015). Rotator Cuff Tendinopathy: Navigating the Diagnosis-Management Conundrum. Journal Of Orthopaedic & Sports Physical Therapy, 45(11), 923-937. doi: 10.2519/jospt.2015.5941

Löscher, S. (2018). 2013 Neer Award: Prädiktoren für das Versagen von nicht operativer Therapie bei chronischen, symptomatischen Rupturen der Rotatorenmanschette. Manuelletherapie, 22(04), 157-159. doi: 10.1055/a-0658-8975