Left Knee Sports injury

Patient: Why does my knee lock out at the extreme of knee flexion? I can comfortably squat past 90 degrees, but when I bend my knee fully, especially with weight on it, the knee locks out and I can’t straighten it without extreme force. When this happens it feels as though my knee has twisted to the outside. When I forcefully straighten it, it feels as though it is popping back into place. A loud popping sound and sensation are occurring. One doctor said I dislocated my knee cap, however, I have a significant meniscus tear in the medial portion. The doctor said he doesn’t know if it is the meniscus flapping into the joint. I was wonder if the meniscus would flap into the joint sooner than the utmost extreme of flexion if it were torn? Please advise. Thanks!

Symptoms: Popping and cracking of knee during movements. knee pain and stiffness. locking out of knee during deep flexion