I've never had knee problems, but if they're constantly hurting through this, you may want to inform your Dr. Knees are nothing to ignore. I know several people who have had knee replacements, even as young as early 40's! Maybe also take a look at the shoes you are wearing and make sure they are durable and fit properly.

Keep up the good work!

I totally understand! I have severe polyarticular rheumatoid arthritis - it effects my knees, wrists, one elbow, and left hip. I am making it through with limited pain though and knees have held up well. Here are my suggestions that have worked for me so far. The thing that makes biggest impact on knees is landing and not bending INTO the landing.. make sure you are bending into your landings so the knees do not absorb the full impact. Also ice the knees after each workout. The Insanity has high impact on joints and that causes inflammation of the joints, knees in particular. Ice is the best anti-inflammatory and you can use it for up to a half hour at a time. I utilize the ice massage method on mine. Get a paper cup and fill it halfway with water, put it in the freezer to solidify (cheap dixie cups work great for this). After your workout, tear the cup down over half to expose the ice and start to rub it all around the knee. Do this until your ice is gone, tearing more down as you need to. Hope this helps!!!