Tendon Feels Acutely Injured After Steroid Injection

A Loyola University Health System study shows that steroid injections cause a tendon to behave in a way where it thinks it has been acutely injured. According to Dr. John Callaci, steroid injection temporarily produces a molecular response in the tissue that is similar to that of a tendon injury, possibly making it more vulnerable to damage during this time.

In the study, Callaci and colleagues examined the global gene expression profiles in rotator cuff tendons following injury or exposure to corticosteroid. The researchers used gene array analysis of the complete rat genome to characterize the molecular response of rat rotator cuff tendon tissue to injury, injection of corticosteroids, and the presence of both injury and corticosteroid.

Results of the study show that 2,000 genes were changed by injury; 1,000 genes were changed by steroids. A significant number, 750, of the changed genes overlapped between the two groups.

From Medical News Today:

Patients who get a steroid injection in their shoulder for rotator cuff pain relief or improved shoulder function should not return to their regular activities or start physical therapy for a few weeks, a Loyola University Health System study shows.
"The implication of an overlapping pathway is that you have pathways that are modulated after an injury suggesting the tendon is doing things to try to heal itself," said Callaci. "That might suggest there might be a temporary period of vulnerability or weakness in a tendon. It thinks it is being injured and it produces things that normally it produces after injury, which might cause some temporary instability."

In conclusion, the team of Dr. Callaci suggests that patients who had steroid injections on their tendon injury should have enough time to rehabilitate. Immediate physical therapy or rigorous activities may cause further damage because the weakened tissue is not able to sustain itself.