It's quite difficult to pinpoint, but it seems be at the back and to the outside/lateral area of the knee (this can be reproduced when I sit with my leg crossed, i.e. when I sit upright on a chair and rest my left foot/ankle on my right knee). I feel no pain when I rub, press or massage the area.

In addition, I feel pain at the back of the knee if I try to do hamstring curls (lifting 23kg), so I stopped. However, it is not as noticeable using lighter weights, but I have ceased doing this exercise anyway.

Thanks.