I got those interlocking 3/4-inch thick foam mats from Lowe's and put it under the area rug downstairs (the floor is engineered tile over concrete). I think the total area I covered was about 8x10 feet. I did this about 6 months ago after working out in an upstairs room for 5+ years. So far, so good. I have not had any knee problems or aches and pains as a result.
You might want to post this in the open discussion forum to get more responses also.