During total hip arthroplasty (THA) procedures, orthopedic surgeons rely on visual and tactile cues to minimize the risk of a limb length discrepancy (LLD) arising from improper implant placement and selection. This paper outlines a novel application of a commercial infrared (IR) motion controller, Leap Motion, to function as an optical tracker of LLD. Additionally, a custom benchtop testing model was used to evaluate accuracy and precision of this commercial IR motion controller against a custom-built IR stereo vision camera. This paper includes a discussion of the algorithms and infrared technology used to image and localize points. The novel design discussed in this paper has clinical applications for a custom-built IR stereo vision setup that will be positioned above the incision site during a THA procedure. Accompanying this solution concept is a fiducial with IR-visible landmarks for quick and accurate point selection and a software algorithm that measures changes between pre- and post-operative leg length.