When there is no weight going through the knee when you bend it e g.
Floor slightly bending down.
The likelihood a given floor has for bending is affected by many factors but the most common primary cause is simply old age.
Warping manifests as gaps between the boards.
How to straighten a warped floor.
Wet down the floor boards slightly.
Dizziness when you bend over is a common occurrence.
Set a cinder block or other large heavy weight on top of the bowed boards.
Sometimes all it takes to get that lightheaded woozy feeling is to look up or down or move your head from side to side quickly.
A new floor design that satisfies code requirements for bearing capacity and rigidity resistance to bend may still be appreciably sloped after many years of service.
Wood responds to changes in temperature or humidity by warping and that can be bad news for your hardwood floor.
When sitting in a chair and moving the knee or standing but with the leg lifted off the floor as you bend it.
If your back hurts when you bend over you should assess the severity of the pain.