I make a big deal out of distinguishing between tendonitis and tendonosis, but it’s perfectly possible to have both at the same time. In fact, it’s likely. Here’s what happens:
You do some repetitive movement for a while and something is not exactly perfectly aligned in your body (i.e., your movement pattern is wrong, etc.) or else you just do the movement so often that your body can’t recover completely. (Recovery issues are particularly important for hard-training athletes and older folks.) This starts to wear down the tendon, causing micro-tears and fraying. This is the beginning of tendonosis, although you don’t notice it yet.
After the damage passes a certain point it triggers a “fix it” response. Your body, trying to repair itself, will cause inflammation to occur, which brings with it the pain that causes you to notice on a conscious level that Something Is Wrong.
This is the point where most people will say, “Hey, I’ve got tendonitis.” From here, a couple of things can happen:
(1) You try to ignore the pain and work through it. Although the most common response, this is doomed to failure and will eventually lead to (2) below.
(2) You take NSAIDs, use ice, rest the area, etc. (the usual prescription for tendonitis).
Now there are two possible outcomes:
(2a) You didn’t have all that much tendon damage to begin with, and what you did have has been repaired to the point that you no longer feel pain. Congratulations, you’re cured!
(2b) You (may) feel some relief from the reduced inflammation, but you still have a considerable amount of pain. This means that while your anti-tendonitis regimen is working on the inflammation, the underlying tendonosis condition is severe enough that it has not been, and still is not being, fully repaired. At this point, further anti-tendonitis measures like NSAIDs and so on are probably not going to help. You need to actively repair the damaged tendons – which is what I cover in detail in my book.