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There are warnings in the literature about tendon ruptures possibly occuring with injected steroids into tendon areas.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1237870/

But there is a family of drugs called the fluoroquinolones, which CAUSE tendon ruptures, and the link to the drug and the event can be as much as a year after using one of these. They are antibiotics for infection.
Cipro (very common) Levaquin (also very common), Avelox, and others.

Many people receive one of these drugs for bronchitis, sinus infections, pneumonia, cellulitis, prostate inflammation, or urinary tract infections. It took many years to figure this out, because of the delay factor. And I have looked on the net for a long time for remedies for this, and because medical experts don't understand how this happens, a solution is still lacking.

These drugs also cause peripheral neuropathy, and it is suspected to be more likely when steroids are used or NSAIDs for inflammation at the same time. Fluoroquinolones are pretty neurotoxic. You can Google them and find websites devoted to their problematic side effects easily.

Think back and see if you were exposed to one of those drugs I listed, in the past before your injury.

It is really difficult to say about the Advair.