If mri and xray came back clean and ra is ruled what else could knee pain with buckling and severe pain for the past year be?

Look outside knee: If knee x-rays, MRI and lab tests are all negative, but knee pain persists and buckling of the leg occurs, look outside the knee for the answer to the problem. Consider a neurological exam, targeting potential pinch nerves from the lower back. Lumbar spine problems, as well as some hip problems, can refer pain to the knee and could also cause leg buckling.

Referred pain?: If the MRI and xray were only of the knee and were truly 'clean', other possible causes include lumbar radiculopathy , or 'a pinched nerve in the back.' a specialty physician evaluation should be able to sort out the cause.