David explains when it’s okay for us to place the knee in front of the ankle in poses like side angle. He also explains when the knee is most vulnerable.
The last three quadriceps muscles are this months muscle(s) of the month. We put them together because these three out of four have similar action and attachments. That is, they are dedicated to the action of straightening the knee (extension).
The rectus femoris muscle is one of the four muscles that makes up the quadricep group of muscles. This is the only one that crosses the hip joint and therefore is related to tight hip flexors. Personally, I have come to find that it is critical in allowing the pelvis to move during backbends.