A hand-made, radiolucent, custom-designed device having a mobile and a non-mobile platforms was used to objectively quantify the in vivo cranial tibial translation, in order to assess the functional status of cranial-cruciate-ligament (CrCL) in dogs. The hypothesis was that changes in CrCL integrity would result in detectable changes in tibial translation. To validate the diagnostic method, data from injured (PA, n = 32), contralateral (CO, n = 32) and healthy stifles (HE, n = 32) were compared. Normalized tibial translation (ΔN) of each stifle was measured in medio-lateral radiographic projection obtained before and during standard thrust force application, in PA (43.59±12.97%), CO (20.32±6.69%) and HE (12.22±3.77%). Comparing PA with HE and CO (ΔN cut-off value: 29.73%), diagnosis could be issued with very high probability. Comparing HE with CO (ΔN cut-off value: 14.80%), high performance was obtained. The translator device could be a useful tool to objectively quantify the in vivo tibial translation in dogs with CrCL rupture, before surgery and during post-operatory follow-up.