Two years ago, I felt a pop while playing football. My physiotherapist said Ihave torn my cartilage and so, he advised me to take rest. It felt good. After 18 months, when I played football again for some half an hour, I felt the pain. So, I visited a different physiotherapist, and he advised me to go with some exercise for a 4-6 week every day. I am visiting him every week. While playing in the pool on Friday, it gave way again, and I could not straighten my legs.