Knee meniscus. To undergo a surgery?

Sir, this is my son writing.The photos attached belong to the left knee joint. Doctor prescribed physio-therepy rather than surgery. After few weeks, the joint was good to jog and play cricket even. But it wasn't​ good enough for Indian squat toilets. A few days ago, i was doing pistol squat with the right knee (i knew i would hurt my left knee, so i dint do with bad knee). After that a few metres sprint. I hurt my right knee badly from inside that there is a lot of swelling around the knee. I cant bend it freely and i can't put pressure on it, like climbing steps up and down. It's like the whole meniscus fluid escaped from between the joints and forming around the knee. Now it looks like my right thigh muscle is beginning to lose the strength, become soft and skinny. Is this case same as my left knee ? Can i regain its strength by physio or do i have to undergo a surgery? Be as clear as possible. Awoid uncertainty! Thankyou