First off let me say that I teach Yoga and not only that, but I try and follow Eddie's stretching instructions from the "Mastering The Rubber Guard" book religiously.
Note: You should never stretch when you are cold. You should only do dynamic stretches and Yoga flow, if you do static stretching cold and are not flexible, you will hurt any part of your body. Think about it,would you throw 400lbs. on a bench and just go for it if you have never lifted before in your life? No...not unless you ride the short bus.
Last year I was rolling with a less experienced guy who jumped guard on me when I wasn't paying attention. I should also add that the mats were totally soaked in sweat. He jumped on an angle and we both crashed to the mats. This is the type of injury I incurred.
YouTube - Charlie Weis injury
I sprained all 4 ligaments in my knee; my medical collateral ligament, lateral collateral ligament, anterior cruciate ligament, and posterior cruciate ligament. I also opened a small tear on the exterior of my MCL(I got lucky there. That is the only tear that has enough blood flow to heal without surgery, but sprains often take longer to heal than breaks do, so that sucks.)
When I went in to see my doctor, he sent me to one of the best Orthopedic Surgeons in Los Angeles.
What did he say after looking at my MRI?
"Wow. Your flexibility saved your knee. I see football players with this type of injury all the time and often times it ends their career."
"Why," I asked.
"It's simple really. They have tons of muscular stability, which is helpful, but they have no joint mobility, or flexibility, so any unusual bending of their knees just tears through their ligaments."
"I am a Brazilian Jiu Jitsu fighter," I said. "My teacher stresses flexibility more than anything else and when he talks, I listen. He is more flexible than a ten year old."
"Well thank him then," he replied. "You are going to keep your knee and return to full mobility, but only because you're so flexible."
It has been nine months. I still feel a bit of pain in my knee because of the tear, but I'm already back to Double Bagging. Thank you Eddie!
When someone tells you that Rubber Guard will fuck your knees up, ask them to show you proof. It's total bullshit. Obviously, if you don't have the flexibility, don't jump right in and start trying the fucking Sorcerer. Baby steps friends. Buy the book.