The pathological noise that causes such a loud popping sound is usually a sign that something is wrong.
Knee injuries can occasionally range in severity from minor to surgically necessary. You won’t be able to be certain until a doctor examines your knee.
Causes knee popping and pain
Although the severity of the injury can vary, it is generally safe to assume that something is wrong if your knee suddenly makes a noticeable popping noise. Here are a few of the potential reasons.
A loud popping sound is one of the telltale indicators of an anterior cruciate ligament (ACL)  tear in the knee, which is typically followed by excruciating pain. It’s possible that you won’t be able to stand or bear weight on the injured leg.