The gait data of freely moving rats were recorded using the CatWalk System (Noldus Information Technology, Netherlands). A compliant run was defined as a run without interruptions or hitches; all limb data were clearly classified. At least one compliant run was collected and analyzed using computer software (CatWalk XT 10) for each rat [18 (link)]. The nanoindentation experiments were performed using a Piuma Nanoindenter (Optics11, the Netherlands), which can locally detect cartilage mechanical properties via indentation using a previously described method [19 (link),20 ]. Ten regions were selected for the indentation test in each sample, including five each for the medial and lateral plateau cartilages.