I’ve written about topical (applied to the skin) capsaicin before, and my take is that creams and so on that contain capsaicin are pretty much worthless for relieving tendon pain.
But there may be some merit to injecting capsaicin into your body in order to provide some temporary relief from pain. In a 2015 study, researchers performed some tendon surgery on rabbits and tested to see whether injecting capsaicin did any long-term damage to the animals. Turns out that 18 weeks after the surgery, the injected group did just as well as the control group in terms of recovery. And the injected group had less pain after their operations.
Of course, it’s only one study. And animal studies don’t always translate into the same results when you try the same treatment on humans. But quite often what works in one mammal will work in another (ie, homo sapiens). ANd hte study was, as far as I can see, pretty well designed.
So if you’re suffering from tendon pain, having a doctor inject you with purified capsaicin might give you some real relief. But of course this is only a temporary fix. Might be good if you have tendonitis (inflammation of the tendon), but long term, it’s not going to help if you have tendonosis (degeneration of the tendon). For that, you’re going to need something like targeted rehab or a program like the one outlined in my book. If you’re not sure which condition you have, feel free to take my quick and easy (and free!) tendon test here.
https://pubmed.ncbi.nlm.nih.gov/26135547/