I've worn these for years, never had a problem with knee/elbow injuries. I don't notice them as particularly hot, but even so, hot would be better than a serious orthopedic injury:

https://www.amazon.com/gp/product/B0773MZQ3G/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Get a set of these:

https://www.amazon.com/gp/product/B0773MZQ3G/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

That and a full face mountain bike helmet have saved my a$$ many times, so much so, that I don't even care what I look like when riding, they work.

Sorry about your wipe-out, and hope you heal-up soon