I got a second opinion on my knee injury about a month ago and decided to have orthopedic surgery with Dr. James Graeter because he's on my health insurance network and that will hold down costs. After he looked at my scans, he told me that yoga poses that are really dangerous for the knee are Ardha Baddha Padmottanasana, Gomukhasana A or any pose in which the knee is flexed sharply. The risk is that the meniscus will be pinched between the femur and tibia bones. In this type of pose, the leg is often rotated and that may put additional stress on the menisci or expose them to the bones in harmful ways. hero's pose (or Virasana) (or variations on it) is another risky pose because your upper body is pressing down on your legs.
Once I understood the knee's peculiar risk in yoga, I realized that precautions have to be taken. For instance, putting a rolled-up hand towel or blanket behind the knee so that the bones are stretched apart. Because you can put your knees at risk in both standing and sitting poses, you have to think hard about how best to wedge the towels between your calf and your thigh.
Because there are no nerves (or blood flow) in the menisci, there's no way of telling if damage happens. It's only when you have debris floating around in your knee bursa that problems develop. It can actually lock up your knee so that it can't move.
