Musculoskeletal changes following non-invasive knee injury using a novel mouse model of post-traumatic osteoarthritis

Summary Objective Post-traumatic osteoarthritis (PTOA) is a common consequence of traumatic joint injury, with 50% of anterior cruciate ligament (ACL) rupture patients developing PTOA within 10–20years. Currently accepted mouse models of PTOA initiate symptoms using various methods, none of which faithfully mimic clinically-relevant injury conditions. In this study we characterize a novel non-invasive mouse model of PTOA that injures the ACL with a single load of tibial compression overload. We utilize this model to determine the time course of articular cartilage and subchondral bone changes following knee injury. Design Mice were euthanized 1, 3, 7, 14, 28, or 56days after non-invasive knee injury. Knees were scanned using micro-computed tomography (μCT) in order to quantify subchondral trabecular bone, subchondral bone plate, and non-native bone formation (heterotopic ossification). Development of osteoarthritis (OA) was graded using the osteoarthritis research society international (OARSI) scale on histological sections of injured and uninjured knees. Results Following injury we observed a rapid loss of trabecular bone in injured knees compared to uninjured knees by 7days post-injury, followed by a partial recovery of trabecular bone to a new steady state by 28days post-injury. We also observed considerable non-native bone formation by 56days post-injury. Grading of histological sections revealed deterioration of articular cartilage by 56days post-injury, consistent with development of mild OA. Conclusions This study establishes a novel mouse model of PTOA, and describes the time course of musculoskeletal changes following knee injury, helping to establish the window of opportunity for preventative treatment.