Hyperextension of the knees happens because some people have loose ligaments and tendons around the knee joint. Often these people have looseness globally. They also may have pelvic misalignment like anterior pelvic tilt, posterior pelvic tilt or hyperextension of the the hip joint (or sway back).

How do I stop my knee from hyperextending?

What causes a knee to hyperextend?

A hyperextended knee — or knee hyperextension — develops when the knee joint bends the wrong way and damages the ligaments near the knee. The condition is common in athletes who play high-impact sports. It can be treated using methods including rest, pain medication, and sometimes, surgery.