From yorkgate road chevin car park walk east along the surprise view footpath for about 400m.
Parallel with the end of the plantation on your right there are some bushes with a patch of heathery grass beneath them. Knottie's stone is visible from the path in those bushes, although the carving is very faint and much easier viewed from the other side.
Worth a look for the view from the stone, with the carved line seemingly pointing at the wart of Almscliffe on the horizon.
Paulus' advice is to visit this one on a wet day and catch it in low sunlight – I managed to visit on a dry February day late in the afternoon when the sun was coming in from the wrong direction. Some of the rings are just about visible and can be traced with a finger but the design is incredibly worn – shame.