There’s one antibiotic that can cause tendon problems. It happened to my daughter’s father-in-law.
That’s Levaquin, it’s known for eat Tendons of older people. It’s also a pretty strong antibiotic that will clear chest and upper respiratory infections. I have taken it a lot more than I should, but a ruptured tendon is better than pneumonia.
I would assume this is what caused McCain’s problem which tells me problems are a lot more serious than reported. Also, he may have stopped Chemo due to an infection.