Frog rocks -- pain in knees

I'm noticing that in the Diamond Frog, Frog and Frog Rock some pain in my inner knees (where the bone meets the floor/mat). I'm doing them using a yoga mat, but even when its folded over twice feel it. Its not so much that it bothers me, I can deal with it 'but wonder if its damaging to the joints and ligaments in any way. Is this something to be avoided? And if so how to overcome it?

 

Thanks 

Hi Eugene, it can be only a problem of pressure, how are you positioning your feet on the floor?

yoga mat is not very thick at least 2 cm mat tickness to protect your knees also contract the glutes while widening your frog 

Thanks Oussama

Alessandro,

I tried them again yesterday and somehow just having a bit more familiarity and knowing what I was doing lessened it. All that remains now are my tight adductors

happy to hear that!