A standardized, open-source, portable model for noninvasive joint injury in mice

Preclinical models of osteoarthritis (OA) are crucial for the study of disease mechanisms and for the development of critically-needed disease-modifying therapeutics. While surgical OA models, such as the destabilization of the medial meniscus (DMM), have been the gold standard in the field for decades, noninvasive joint loading-based models have increased in popularity and utility. To facilitate standardization of the noninvasive anterior cruciate ligament rupture (ACLR) model in mice, we present the Mo bile J oint-Injury O perator (MoJO) - an open-source protocol with accompanying fixtures and data, designed for a low-cost, commercially-available, portable uniaxial testing system with a small footprint. We provide 3d-printable fixture designs and a rapid, highly-repeatable ACLR-mediated joint injury protocol that results in the expected post-traumatic osteoarthritis phenotype in male and female C56Bl/6 mice. We then describe the expected mechanical data from the injury procedure and offer various troubleshooting strategies. Finally, we summarize the resultant PTOA phenotype by knee hyperalgesia testing, µCT imaging, flow cytometry, and histological assessment. Increased standardization of this model is a critical aspect of the overall refinement of animal models of OA.