I recently had a patient ask me where a flu shot should be administered. This may seem like an odd question since I am a Doctor of Physical Therapy and not a family physician. However, the reason she asked is because she had received another type of shot 2 weeks prior and her left shoulder had been painful since. She was due to have a flu shot and was concerned that her shoulder would be re-aggravated.
With flu season quickly approaching and because my patient asked me about this, I felt compelled to address an unfortunate situation that has occurred at least 3 times in recent years. I have cared for patients who received a flu shot only to discover shoulder pain within minutes to hours after the injection. Their pain persisted and ultimately resulted in a trip to the orthopedist and a prescription for physical therapy.
Flu shots are typically administered in the meatiest or thickest portion of the deltoid muscle of the upper arm. However, on rare occasions, the person administering the flu shot selects a region of the muscle closer to the shoulder joint. The three patients I have seen who required physical therapy after a flu shot ALL described receiving the flu shot closer to the shoulder joint instead of in the thick muscle region of the deltoid.
I suspect the reason they had shoulder pain immediately after or within hours of the flu shot was because their shoulder joint became inflamed from the injection. All three patients presented with symptoms associated with shoulder impingement (when the rotator cuff tendon gets pinched within the shoulder joint space). They described pain with raising their arm overhead, behind their back, and out to the side. They demonstrated a lack of movement and weakness due to sharp pain with specific movements. All patients successfully completed physical therapy and returned to normal activities within just 2-4 weeks.
So, should a flu shot cause shoulder pain?
I’ll answer that in two ways - YES, your upper arm will be sore because the muscle was injected with the flu vaccine. It will feel bruised and may be sore to touch. I recommend applying ice to the area to reduce the soreness. NO, your shoulder joint should not be sore and painful IF the injected vaccine was administered into the meatiest portion of the deltoid muscle.
What can you do when you go to get your flu vaccine?
Enjoy the Autumn Season and Stay Healthy!
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