Shoulder pain after breast cancer: Muscle strain or something else?


Every second person after having breast cancer experiences long term adverse shoulder and arm problems. I am wondering whether a new realization in the athletic population, that injuries or pain can be the result of injuries of the tendons or connective tissue injuries, can help us better manage this problem.


Can this be the case after breast cancer?


Can we prevent or minimize chronic shoulder pain from happening amoung so many breast cancer survivors?


I know that we're not there yet; we're not offering best after care and recovery support for people after breast cancer. To better help people recover after breast cancer, we need to understand the potential root of pain and dysfunction, so we can treat painful problems and more importantly trial new ways to prevent these conditions from occurring.


I believe the following two research papers help to clarify a new focus for the underlying cause of pain and injuries and that health professionals are in a position to take action with new interventions for breast cancer survivors.


The first paper I want to share with you is a review of 16 studies that reported on lower limb sprain type injuries in an athletic population. The researchers investigated the nature of the soft issue injures that brought people to medical care: muscle strains, tendinous injuries or injuries of the connective tissue between the muscles.


They found that only 1:8 of the injuries were reported as muscle strain and a whopping 68% of the cases had injuries at the junction between the muscle and the tendon or at the tendon. This finding of more “white” connective tissue injury, compared to the red muscle injury, offers an interesting refocus to the nature of injuries and pain.


The study of fascia has exploded over the last 5 years because of new imaging technology and dissection methods. We now can view the much finer fascial or connective tissue as important networks that surround the muscle, allow free glide between muscles and connect muscles via tendons and enveloping and connecting fascia to other muscles across the body.


To work out the level of safe stretch and the level of harmful stretch: where stretch causes micro tears, increased fibrosis ( thickening) and rupture, researchers are investigating how these different tissues respond to stretch. The general finding is that muscles require about 5 times the amount of stretch, from the rested position, to go beyond their elastic capability into the phase where micro-tear can occur, when compared to a tendon.


Tendons and one would suspect the much finer fascial connective tissues surrounding the muscle have been found to micro-tear and rupture at much, much, lower forces. This makes sense when you think about it, when you do something that is a bit more strenuous, the aches last a couple of days- which means that it’s likely a strain of the connective tissues and not a tear of the muscle.


Unfortunately most of the stretch testing is done in laboratories where the tissues are either taken from animals or cadavers. They cut out a tendon or cut a portion of muscle and stretch it between vice type machinery.


This type of “out of body” testing does not consider the complexity of the body’s soft tissue connections and the ability to absorb and transmit forces. However the results of the investigation into the incidence of tendon and connective tissue sprains and muscle strains for sportspeople, does seem to support this model of varying levels of stretch and strain for tendons and muscles.


The higher presentation of tendon injuries in the athlete study, suggests that damage to the fascia happens more readily than damage to the muscle in real life settings. Another way of combining these new ideas and findings is this hypothesis: the tendon or musculo-tendonous injuries that lead people to pain and then requiring treatment can be from lower levels of stretch to the tissues. So it might not take a big injury to cause changes and damage to the fascial connective tissues of tendons for example, as compared to the muscle.


Does this same mechanism of injury to the connective tissues occur in people after breast cancer?


This year, a new investigation into the connective tissue changes present in people who have shoulder pain after breast cancer helps us better understand this important question.


In 2019-2020 a team of researchers investigated the ultrasound changes seen at the shoulder. Fifty two women who were relatively young (55 years- mean age) , on average 4 years after their surgery and had experienced pain, rated on average of 4/10 for 1.7 years (mean), had their shoulders closely looked at by radiologists. The aim was to identify if there were soft tissue changes on the painful side compared to the non- painful side.


They found the top three common abnormal ultrasound findings were:


· biceps tenosynovitis ( tendon ),

· supraspinatus tendon partial tear, and

· adhesive capsulitis ( shoulder joint connective tissue)


Each of these injuries represents thickening, inflammation and then micro tear to the connective tissues of the shoulder.


The causal factors and therefore the standard treatment strategy for chronic shoulder pain after breast cancer surgery hasve not yet been established. But one simple way of looking at these ultrasound findings is: some people are experiencing over- stretch and strain at the shoulder resulting in significant tissue changes.


By this stage you would be laughing at this basic and simple statement. As most women with pain, know they experience stiffness and that they can’t stretch their arm and chest as much, anymore.


It’s not a hard leap to understand that more inelasticity in the chest and upper arm muscles means that strain injuries can happen more readily. Less stretch in the soft tissues means the forces applied through the body, from doing ordinary day to day tasks, cannot be absorbed or transmitted as well as it did before surgery and before radiotherapy.


And when we look at the location of the strain injury presentation- it’s the tendons and local white connective tissue of the joint. MATCH! to the more likely chance of strain injuries being of tendon and connective tissue over muscle injury findings from the first paper we considered, with the athletes.


Are people after half the people after breast cancer engaging in athletic endeavours? I don't think so.


What can be the causes for tendon and connective tissue overload or strain after breast cancer?


There is clear evidence that the pectoral muscle becomes stiffer after radiotherapy and especially after axillary lymph node removal. The pectoral muscle underneath a mastectomy does not stretch as much, when energy is passed through it, especially when compared to healthy matched controls (people).


Also the pectoral muscles have been found to become smaller in volume than the other shoulder muscles. This change in size happens over time, after surgery and radiotherapy and only happens at the chest muscles, not at the other shoulder muscles.


We also know that extensive scarring can result from breast surgery. In some people extra scarring happens and this can be the cause of adhesions forming between the skin and the muscles. These scars and adhesions can change how these soft tissues of the chest respond to stretch; what we see is less glide and less distance that the arm can move.


Do these new findings help health professionals?


My personal opinion is YES and here are my thoughts.


1. Not all people after breast cancer have pain and movement problems- but at least 50% do, that’s every second person, and we need to help them!


2. Arm exercises need to be carefully selected so that the tight chest, the upper shoulder muscles and the connective tissues are not stretched beyond their elastic capabilities. Exercising to lengths that create micro-tearing should be avoided.


3. The stiffness and lack of glide in the chest area must be addressed. Therapists need to help women ( and men) address and self- treat both the scar tissue at the surgical sites

( skin and deeper) and the radiotherapy stiffness at the chest muscles.


4. There needs to be a surveillance and rehab pathway to assess for and treat chest and arm tightness, when it presents- and not wait for tearing or chronic shoulder pain to occur.

What can you do, if you've had breast cancer surgery and radiotherapy?


Maybe wait for the research to scientifically prove that certain rehab treatments will free up the chest muscles to make them stretchier and less stiff.


Maybe find an oncology rehab health professional, to assess and treat your shoulder / arm stiffness.


Or if there is no one trained in your area, you can connect with me online, as we can do quite a bit together, to help reduce chest and arm stiffness.





Whatever you do, don't wait for your Doctor to refer you to an oncology therapist, because only about 6% of people who are experiencing pain after breast cancer are referred to pain management services.


Connect with me by email if you want to book an appointment online or face to face, or discover ( 15 mins) whether you have a problem that is worth investigating.

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