When you feel your knee is giving out, meaning that suddenly the knee feels unstable, it is usually due to a ligament injury. A ligament is a short, tough band of tissue that connects two bones.

You doctor will also feel your knee, checking for pain, warmth, and swelling. They will then bend, straighten, rotate, or press on the knee to feel for injury and find out how well the knee moves ...

Knee buckling is when one or both knees feel weak and give out. It can be accompanied by pain, but not always. If it happens a lot, it could be a sign of an underlying medical condition.

You feel no pain in your knee when you walk, jog, sprint, or jump. Your affected knee is as strong as your healthy knee. How to Prevent Runner's Knee.