Like Sue22 said, some tendons just shouldn't be injected. I can't be sure that the injection caused the rupture, but since that happened, I'm 90% sure that was the cause. I was 6 weeks post steroid injection, pain had just started up again and I had made an appt for another injection. While moving a chair in the kitchen, wearing supportive shoes, I heard an audible 'snap', felt searing pain and couldn't put my foot on the floor and have it support my weight. Instead of another shot, I got a cam-boot for 4 months and then surgery.
If you look at research...there are a lot more people saying don't inject achilles tendon or plantar fascia because of the risk of rupture. On the other hand, I had an injection of the other heel which didn't lead to rupture (but it didn't lead to healing, either) and I had surgery on that heel 2 yrs later. I don't think it's worth the risks, just my opinion, though.
