Devices and methods for providing in vivo performance measurements of an orthopedic implant involve an orthopedic implant having at least two radiopaque markers associated with a movable portion of the implant. The markers are positioned at known locations and in a first known and predetermined relationship to each other. The markers provide visible references upon application of a medical imaging technique to show the relative position of the markers according to a second, changed relationship to each other after implantation of the orthopedic implant. At least one measurement of performance of the implant can be determined from the first and second relationships of the markers.