On July 4th, while at my son's house, I did something to a knee that left me somewhat painful. Don't know what exactly I did, but I think that it may have happened while chasing Jemma through the backyard. At any rate, I listened to my body and did not attend yoga during the following week (last week).
I was back in class last night, and George really put us through our paces. He is one fine teacher. By the time I arrived home, I realized that a week off does not work for a 68 yo body. You need your fix frequently to stay limber. Today, I am a bit sore. He was concentrating on our hip flexors, so the hips/low back are speaking to me, and my shoulders are telling me that I have not done a headstand for over a week.
Of course, if your knee hurts when you bend it, you can't do standing poses or inversions too well. Oh, well ... get over it and go on. I did.