I have to switch between multiple anti-inflammatories as my body seems to adapt to what I take to manage chronic arthritic pain
Have you looked into prolotherapy before? (sugar water injections)
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The idea is that it acts as an irritant which increases blood flow and other healing responses to that area. Tendons in particular are thought to heal slowly because they don't have great blood flow. This strikes me as similar to the ideas of dry-needling and platelet-rich plasma injections.