Anecdotally and with no knowledge of your situation, I agree with CFB. I started a program of core strengthening with emphasis on the posterior chain (and the posterior) after a serious lumbar disk situation and it really helped me with position on the bike, strength, and standing up and walking pain free like an athlete again. Cyclists typically have weak glutes and you can crack an egg on my ass now.

Real SI arthroses are rare, according to conventional medicine, and pain from quadratus lumborum strain, which is common, locates near the SI joint. The QL is part of that posterior chain and is protected and supported by the glutes.

Good luck!