An Acute ACL Rupture in Knee Joints of Female C57BL/6 Mice Results in Whole Bone Loss Driven by an Increasing Osteoclastic Activity

The anterior cruciate ligament (ACL) stabilizes the knee and resists forward displacement of the tibia relative to the femur. ACL injury rates in the young are increasing, with ~50% of patients developing knee osteoarthritis within 10 years. Adolescents are six times more likely to suffer an ACL graft failure within the first five years of reconstructive surgery than adults. Using an in vivo ACL rupture animal model, we investigated the physiological response to injury within the bone, ligament, and synovium of the knee. Previously, the Schlecht Lab showed significant bone loss within the ACL attachment in young adult female patients. Consequently, we hypothesized that bone loss would be greater at the enthesis compared to the whole joint due to localized disuse osteoporosis. To test this, ACLs of adolescent C57BL/6J inbred mice were ruptured in vivo, followed by euthanasia across multiple post-rupture time points. The loaded and non-loaded knee joints were then three-dimensionally imaged with micro-computed tomography (µCT) and processed for immunohistochemistry. My role has been to 1) validate µCT region-of-interest selection, 2) perform general staining and immunohistochemistry, 3) image and quantify antibody presence in tissue sections, and 4) conduct gait analyses and quantify video-captured gait pattern fluctuations.