Left knee pain and sound. It be treated?

I used to drive for 100 kms daily. I got stressed my knee due to repetitive clutch movement. It started paining in my left knee initially. Now the whole leg became weak. I am not able to sit or stand for a long time. I feel a sound in my knee when I bend my knee in-out by lifting my leg up. This sound doesn't resemble the sound most of the people get when doing squats. I also feel pressure in my knee below kneecap from outside. I consulted well known physios but their treatment doesn't help. I went for a knee x ray which showed normal cartilage. Is there any thing I can do to get the sound out of knee and strengthen my legs as before. It's almost a year since am facing this issue. Are there any tears in ligaments or tendons? If so how can it be treated? Any help is appreciated.