Bulletproof knees by Mike Robertson. I've been dealing with issues with my left knee for around 4 months now and two days into the first phase of the recovery program covered in this book and i'm feeling dramatically better. It's expensive ($100) but totally worth it for recovering from knee issues or preventing knee issues, you'll be doing stretching, foam rolling, mobility work strengthening exercises as well as improving muscle recruitment to keep your knees healthy. Definitely something to check out most people have shitty hip and ankle mobility as well as not having optimal glute function.