When your shoulder hurts, it would be nice if there was something quick and easy to help get rid of the pain.
To many, shoulder injections seem to be one of those solutions.
Historically shoulder injections have been believed to be an effective and common treatment for shoulder pain. Research shows that 96% of clinicians believe shoulder injections are helpful (Johansson, K. et al. Br, J Gen Pract 2002) and 22% of MD’s will offer shoulder injections as the first treatment for shoulder pain (van der Windt, DA, et al. Ann Rhuem Dos 1995).
But is this actually best practice? Does the research prove shoulder injections work? Is there any harm in getting a shoulder injection?
That’s what I want to address for you today.
Injecting medicine directly into your shoulder seems logical. If your pain is caused by inflammation, and you can inject something to reduce the inflammation, then it makes sense to inject the tissue with an anti-inflammatory. It makes more sense than taking an anti-inflammatory pill like Aleve, because shots can concentrate the medication right to the source, which should make it quicker and more effective.
It’s a simple procedure, takes way less time and effort than therapy, and on the surface it seems like there is not much risk. But we need to explore this further.
Let’s dig into the evidence to investigate whether shots are a good thing for your shoulder.
What is being shot into the shoulder?
Most injections are corticosteroids, which are anti-inflammatories. Other substances include lidocaine, saline, sugar water, or platelet rich plasma.
Where are these substances being injected?
When injecting into a shoulder, the idea is to inject into the joint space. Sometimes the tendon or bursa are the target. However, a substantial body of evidence recommends against injecting the tendon, as this leads to tendon damage and poorer outcomes (Cook, Lewis, JOSPT 2019). Many clinicians will rely on imaging to assure the intended target is hit. Interestingly, there is debate whether injecting substances locally (in the shoulder) is better than systemically (in the buttocks) (Ekeburg, OM. BMJ 2009).
Do they work?
In general, the evidence for the effectiveness in injection therapies to reduce shoulder pain is not very strong. The effectiveness does depend on the substance being injected.
For corticosteroid injections, which are the most commonly used and researched, a recent meta-analysis concluded that they provide, at best, minimal pain and short term relief in a small number of patients. Only 1 in 5 patients experienced mild relief, and when this did occur, it lasted only a few weeks. (Mohamadi, A. Clin Orthop Relat Res. 2017). This is consistent with several other systematic reviews showing inconsistent outcomes, and if there were benefits, they were short term (Cook, T & Lewis, J. JOSPT 2019)
For Lidocaine Injections (local anesthetic) have been proposed due to having less negative side effects as cortisone injections. Also, it is suspected that anesthetics reduce tenocyte numbers, which may have a therapeutic effect given increased tenocyte numbers are associated with tendinopathy. Unfortunately, there are no randomized control studies comparing lidocaine injections with and established sham injection. There is evidence however that shows lidocaine injections are less effective than corticosteroid injections in the short term. (Cook, T. et al. Br J Sport Med 2018).
For Saline Injections, only 2 studies have been done comparing saline injections with cortisone injections, and both did not show a significant difference. These studies were of poor methodological quality so it is difficult to make strong conclusions at this time. (Cook, Lewis, JOSPT 2019).
For Prolotherapy, which uses a hypertonic dextrose solution (or sugar water), 1 study showed better outcomes compared to saline injections (Bertrand, et al Arch Phys Med Rehab 2016). Two other studies showed better results compared to convention care or exercise ( Seven MM, et al. Orthop Traumatol Surg Res 2017, Lee DH, et al Arch Phys Med Reabil 2015) However, these studies failed to include a sham control group to rule out placebo, and also failed to detail the nature of the exercise involved. In one study, exercise intervention was for only 3 months. More high quality studies are needed to determine the effectiveness of prolotherapy.
For PRP (Platelet Rich Plasma) injections, the research is sparce and of too few subjects to be regarded as a powerful enough treatment to make strong conclusions. A systematic review investigating the research that does exist showed a small to negligible effect. (Miller LE, et al BMJ Open Sport Exerc Med 2017)
What’s the harm in giving it a shot?
Even with the limited evidence showing it can be effective, does it hurt to try? That’s an excellent question given the fact that shots are simple, quick, and require little time and effort of the patient, especially in comparison to the alternative treatments like physical therapy.
My answer in the past has been to suggest patients to give it a try, as the downsides seems low. However, based on the recent evidence, my opinion has changed.
One of the biggest risks of using a trial of an injection is when doing so leads to the patient to falsely conclude that they need to try only the shot to determine its effectiveness, and stop pursuing other effective therapies. This is similar to a false choice fallacy, where they may be restricting themselves from a treatment known to help a wide range of issues pertaining to their shoulder in order to pursue the treatment of the shot.
In short, my only concern about advising a patient to receive a shot was from the fear of them excluding other potentially more effective strategies. If the injection was done in conjunction with another treatment, then it should be a fine pursuit. But again, recently my opinions on this have changed.
Cortisone injections have been suspected to cause damage to tendon tissues.
Several studies have shown that corticosteroid injections have negative effects on the rotator cuff (Cook T, Lewis J, JOSPT 2015). One study found a 17% incidence of full thickness tears in patients who received corticosteroid injections at 12 weeks follow-up (Ramirez J, et al. Mod Rheumatol 2014). Interestingly, the same study showed a significant reduction in pain, which is consistent with studies showing a lack of clear correlation between pain and the extent of tendon damage. However, the study was not designed to include a control, thus it was not possible to determine that cortisone injections cause these tears or the pain relief.
The risk of tendon rupture following injection has been well known. However, the dosage of cortisone required to cause that risk is not well understood. Accordingly, there is concern, but no consensus, regarding the negative effects of cortisone injection therapies on rotator cuff tendons.
It makes complete sense that cortisone increases risk of further tendon damage. Corticosteroids cause tissue break down. Given that tendon related pain seems to be associated with tendon degeneration, increases the risk of more tendon degeneration should be avoided.
Based on this evidence and known physiology of the tendons, it seems that cortisone injections should no longer be thought of as a risk-free option, especially given the limited evidence showing its effectiveness.
What about the risks of the other injections, like prolotherapy or PRP?
One clear risk is the damage it may do to your bank account. Most insurance companies will not reimburse for these shots. That means you’ll likely be paying $600-$3000 per injection, with multiple injections suggested, and that’s not including consultation and other fees.
Another risk is that advocates for PRP claim you should avoid exercise therapy for several weeks supposedly on account of allowing the best outcome from the injection. This is not based on strong evidence and may encourage people to stop or interrupt receiving evidence based care such as exercise.
Cook points out that since degenerative tendons demonstrate an increase in tendon cells, and increase in more stem cells in a hypercellular environment may impair the ability to recreate a normal cell to matrix relationship, rather than help. (Cook JL, et al B J Sports Med 2015)
Other risks are not yet known, as more studies are needed. However, given the substances involved, there does not appear to be strong concern for negative effects on tendon tissue.
Why don’t injections work?
Sometimes it helps to understand purported mechanism of effects of a treatment, even if you have proof that it doesn’t work. Especially when it seems on the surface like it should work!
There are several reasons why it actually makes sense that injections don’t work when you dig deeper.
1. Many shoulder problems are not inflammation problems
Contrary to common opinion, tendons in painful shoulders often are not inflamed. When tissue samples are taken of these tendons, they often lack inflammatory cells. (Cook JL, Purdam, CR. Br J Sports Med 2009. Rees D, eta al Br J Sports Med 2014). That is why many researchers and clinicians are now referring to these conditions as tendinopathies, not tendonitis. The suffix -opathy refers generally to damage or pathology, whereas -itis refers to inflammation.
Thus, it would make sense that an anti-inflammatory medication wouldn’t have an effect on an -opathy condition. Part of the issue is a semantics problem. Many people use the word inflamed to mean irritated. Physiologically, an inflamed tendon would respond to an anti-inflammatory, while an irritated tendon may not. Given that ‘irritated’ would describe a painful tissue where there is pain, regardless of the mechanism, describing it as irritated may be best to avoid confusion.
2. The cause isn’t being addressed.
Whether or not something is effective at reducing pain, if you don’t fix the cause, the problem will likely return. Injections do not address the cause: they don’t make tendons more resilient, muscles stronger, your brain more effective at putting your shoulder in more advantageous positions, improve your ability to manage load by modifying habits related to over use, increase joint mobility, etc. Getting an injection without addressing the cause is like taking Tylenol for a headache then banging your head against the wall. Always start with addressing the cause.
3. You can’t tell what tissue to target.
Tendon, labrum, and joint damage is incredibly common in people without any pain or problems. (Sher J Bone Joint Surg Am. 1995. Miniaci, A Am J Sports Med. 1995). So finding damage on an MRI then targeting that tissue with in injection is often faulty reasoning. It may not be possible to determine which tissue is the source of the pain and many times multiple tissues are involved. Sometimes, tissues outside of the shoulder are the culprit, such is with referred pain from the spine.
4. Tendon regeneration isn’t needed to reduce pain and improve function.
For therapists attempting to regenerate tendons, they could be barking up the wrong tree. Many studies show that pain resolved and function is restored, even when the imaging shows there is no change in the tendon damage! (Abtahi, A, et al World J Orthop. 2015 Mar). Alternatively, researchers suggest that it may be the non-injured parts of the tendon, or adjacent structures, that adapt by becoming strong and more resilient, thus successfully compensating for the damage (Docking SI, Cook J. Scand J Med Sci Sports. 2016)
5. Single factor treatments rarely fix multi-factorial problems.
In over 2 decades of treating injuries, it’s hard to recall many times when only one thing was causing someone’s pain. Most clinicians will see this as well. Researchers lament this, as studies often fail to prove a treatment works in isolation, yet when applied in combination with other factors, it is more successful.
Let’s take a simple case of overuse. You haven’t thrown a baseball in years, and now you have a son who is starting little league. Now you are throwing hundreds of times a week, and your arm hurts. The best exercise program in the world will often fail if you continue to over-exert your arm. Thus, treatment must address activity modification, as well as other treatments such as strengthening, motor control and mobility exercise.
I’ve tried everything else and that didn’t work either, so is trying an injection really a big problem?
This line of thinking makes sense. When you try something and it isn’t working, why not try something else, even if it is a long shot?
In spite of the evidence suggesting in favor of exercise therapy for treating shoulder pain, some will still fail these treatments (Kuhn Am J Orthop. 2016 Feb). Given the time and effort in following exercise protocols, when it doesn’t work, injections seem much more attractive. Even if the evidence isn’t great and there are risks. But this can turn our attention from the real problem.
Exercise therapies that don’t work are usually due to 5 things:
1. A misdiagnosis: Many people presenting with shoulder problems actually have neck or mid back issues. Even the best treatment targeted at the shoulder will not only be ineffective, but it might make things worse, as exercises intended to stress muscles or tendons of the shoulder will overwhelm irritable disc, nerve, or joint tissues of the neck. Also, not all shoulder pain is the same. Some are related to joint damage, others are related to tendon damage. Some are related to stiffness, other related to instability. Some are related to weakness, others due to overuse. The treatments required for these issues differ greatly.
2. Doing the wrong exercises. Related to the above, many people are simply doing the wrong exercises. A common example is doing band eternal rotations. While stronger shoulders may tolerate this, an irritable shoulder will often get more irritable. This is because the tension of the band increases as it is stretched when you move further into external rotation. However, the muscles are often weaker the farther you move them into external rotation. This mismatch may trigger more pain, inhibition, and irritation for a damaged tissue.
A similar example is with dumbbell lateral raises. While these are excellent exercises to strengthen healthy tissue, they will often overwhelm irritable tissues, even with very light weights. This is because the long lever of the arm increases the torque on the shoulder. It takes time to build the shoulder tissue resiliency. Failing to appreciate that is like giving calculus to a first grader.
However, by using a pulley that allows for the application of small, incremental loading, the stress can match the variable strain curve, while also applying a load capable of improving resiliency but not exceeding the irritability threshold.
In addition, exercises that are critical for daily function and well tolerated by even irritable shoulders are often not prescribed, like rows, pull downs, and pushing exercises. Since these exercises emphasize force production from the “proximal” muscles like the back and chest, with smaller lever arms, even severely damaged tissues can tolerate these movements provided they are dosed properly. Applying these exercises can help restore function faster.
3. Doing the right exercise wrong. Proper technique is critical for challenging the targeted tissues, ingraining proper motor patterns, and minimizing unintended damage and irritation. Unfortunately, poor technique is very common. This is due to either improper supervision, not appreciating how long it takes for people to properly learn exercises, or simply not knowing how to do the exercises. For example, subtle swaying of body weight while doing external rotation will take the stimulus completely away from the rotator cuff. This is because the rotator cuff is very small, and the large weight of the body can move the small resistance intended for the small rotator cuff muscles. It’s like the older sibling that keeps shouting out the answers to the little ones basic math homework, robbing the younger one of the stimulus to adapt.
4. Not sticking with the exercises long enough: Exercise has many therapeutic effects: it helps deliver nutrients to tissues, inhibits pain, ingrains motor patterns to optimize force production and properly distribute load, and improves tissue resiliency. It is this last effect that takes the longest to manifest. Making tissues like tendons more capable of tolerating strain can take 12 weeks to 24 months (Bohem S,et al. Sports Med Open. 2015. Yang G, at al Birth Defects Res C Embryo Today 2013). Such adaptations may be what is needed in order to tolerate stresses inherent to functional tasks without pain. If treatment is stopped before the tissue has enough time to sufficiently adapt, tolerance will not improve, pain and functional limitations will persist, and treatment will be wrongly considered a failure. Thus, it is important that treatments designed to make tissue more resilient be carried out long enough to be able to produce its desired effect.
Unfortunately, treatments are rarely provided for sufficient duration mostly because clinicians pander to the frustrations and desires patients have for quicker, easier solutions by offering riskier and less effective options that require less work from the patient, less time for both the patient and clinician, and more profit for the clinician. The evidence, however, leads us in a different direction. Repeatedly, exercise has shown to have a substantial effect on improving tissue resiliency, and that it takes much more that a few weeks to see these effects fully manifest.
5. The tissue is unable to respond to loading: Too often patients are told to do exercises that apply too much load to damaged, irritable tissues. This can be hard to appreciate for both the clinician and the patient, as the exercises do not seem to be very difficult and little to no external weights are involved. For example, someone with a partial supraspinatus tear may be advised to do scaption raises with no weight for 3 sets of 12 reps. However, with each rep more and more pain is provoked, causing compensatory motions and increased irritability with each repetition. This can be quite frustrating, especially since no weight is involved, and even a partially torn tendon should be able to tolerate some loaded to heal and get stronger.
Related to point 3, this is more of a dosing problem versus selecting the wrong exercise. For example, active assist range of motion by applying a counter weight through a pulley will offset some of the weight of your arm at a critical part of the movement (usually mid-range of motion with the force requirement to elevate your arm is highest). This may allow you to move with less pain and irritation, yet still provide some stimulus to initiate loading critical to healing.
Final verdict, should you get a shoulder injection?
Given the low likelihood that it will provide a positive result or superior results compared to other treatments, as well as the risk of harm to tendons in the case of corticosteroid injections, I do not recommend those with shoulder pain receive injections. Coupled with the known need for tendons to require loading to heal, and the likelihood that injection either impairs this capacity or fails to address this mechanism, it is not promising that injections will emerge as a good treatment option.
An exception is for those with adhesive capsulitis, aka “frozen shoulder”. Cortisone injections may provide relief for up to 24 weeks in such cases (Koh, KW Singapore Med J. 2016. Xiao RC Clinical Journal of Sport Medicine: May 2017.) Some evidence suggests that when coupled with manual joint mobilization, corticosteroid injections may provide superior results in the short term (Cho C, et al. Clin Orthop Surg. 2019). Given this population rarely has tendon damage, they may be at less risk of tendon damage. Also, the risk may be justified as there is an inflammatory component in this condition, and the pain relief provided by the anti-inflammatory effects on the injection may allow for better tolerance of the mobilization which is proven to increase mobility.
Other than this circumstance, the evidence does not support the use of injections for the treatment of shoulder pain.
Instead, focus on activity modification, exercise, and joint mobilization as your primary strategy for treating shoulder pain.
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