Dislocation under my knee 3 years back. but i experience pain in my ankle for some seconds when i put effort ever since. xrays found nothing. ?

Kinetic chain issue: With a history of a knee injury on the same side, I suspect that there are some muscular imbalances between each side of the body and from bottom to top-Kinetic chain. Parts of your body do not work in isolation, but work in groups and coordinate together. Seeing a Physical Medicine and Rehabilitation specialist could pinpoint the issues and target treatment to better resolve your ankle issue.