AJSM Webinar Series: ACL Injury and PTOA: Bridging Biology, Imaging, and Machine Learning to Improve Outcomes-Retzky JS et al. Early Anterior Cruciate Ligament Reconstruction Mitigates the Development of Posttraumatic Osteoarthritis in a Murine Model. AJSM 2026. PMID: 41476416

Retzky JS et al. Early Anterior Cruciate Ligament Reconstruction Mitigates the Development of Posttraumatic Osteoarthritis in a Murine Model. AJSM 2026. PMID: 41476416

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This murine study examined whether the timing of anterior cruciate ligament reconstruction (ACLR) affects the development of posttraumatic osteoarthritis (PTOA) after ACL rupture. Fifty-five male mice were assigned to four groups: uninjured controls, ACL rupture only, immediate ACLR, or delayed ACLR performed 7 days after injury. Outcomes at 28 days included cartilage degeneration by OARSI histology, knee range of motion (ROM), gait, immune cell responses in the ipsilateral iliac lymph node and spleen, and bone volume by micro-CT.<br /><br />The main finding was that immediate ACLR reduced PTOA compared with delayed ACLR or no reconstruction. Mice with ACL rupture only and those with delayed ACLR showed significantly worse femoral and tibial OARSI scores, indicating more cartilage degeneration. In contrast, immediate ACLR produced histological results similar to uninjured controls and significantly better than delayed ACLR. Delayed ACLR also had lower proximal tibial and distal femoral epiphyseal bone volume than immediate ACLR.<br /><br />ROM was reduced in both reconstruction groups early after surgery, but by 28 days immediate ACLR had recovered to control-like ROM, whereas delayed ACLR still showed stiffness. No meaningful differences were seen in pain-related gait measures among groups. Surgery increased local immune cell numbers in the draining iliac lymph node, but splenic immune responses were unchanged, suggesting the inflammatory response was localized rather than systemic.<br /><br />The authors conclude that early ACLR mitigates PTOA in this mouse model. They suggest that ongoing joint instability and persistent hemarthrosis before delayed surgery may contribute to worse cartilage and bone degeneration. Clinically, the study supports the idea that earlier stabilization of the knee after ACL injury may help reduce later osteoarthritic damage.

Keywords

anterior cruciate ligament reconstruction

posttraumatic osteoarthritis

mouse model

ACL rupture

immediate reconstruction

delayed reconstruction

cartilage degeneration

OARSI histology

knee range of motion

immune response