Almost a week ago, I put my left foot on my sofa and my right knee then buckled. I caught myself by falling onto the sofa. It didn't hurt much but started swelling about 1 hour later. I was able to walk but it was difficult to maintain balance and I've been using a knee brace and the RICE method since then. The swelling and pain is almost gone but I've noticed that the left side of my knee moves to the right when I walk and makes it seem like it will buckle again. Do you think I tore a ligament?