I Had A Knee Replacement And Currently Going Thru Pt...I

I had a knee replacement and currently going thru pt...I was doing great little pain and great motion...recently sat on a low toilet and couldn't get up...however when I tried I got an extruduating pain like something snapped or tore inside...it was like a chain saw went down the inside of the knee. .now I have a let of burning and pain when sitting and getting up from a chair. I have been icing it but no relief..can something tear inside the surgery was 11/5/15