AJSM Webinar Series: ACL Injury and PTOA: Bridging Biology, Imaging, and Machine Learning to Improve Outcomes (Recording)-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 controlled laboratory study examined whether the timing of anterior cruciate ligament reconstruction (ACLR) affects posttraumatic osteoarthritis (PTOA) after ACL rupture. Fifty-five male mice were randomized to ACL rupture only, immediate ACLR, delayed ACLR (7 days later), or uninjured controls. Researchers assessed cartilage degeneration histologically using OARSI scores, along with range of motion (ROM), gait, immune responses in lymph nodes and spleen, and bone volume by micro-CT.<br /><br />The main finding was that immediate ACLR significantly reduced PTOA compared with delayed ACLR and untreated ACL rupture. Mice in the delayed ACLR and ACL rupture groups showed greater cartilage degeneration in both the femur and tibia. In contrast, immediate ACLR produced histologic scores similar to uninjured controls. Delayed ACLR also resulted in lower bone volume in the proximal tibial and distal femoral epiphyses than immediate ACLR.<br /><br />ROM testing showed that both ACLR groups had reduced motion early after surgery, but by 28 days the immediate ACLR group recovered ROM similar to controls, whereas the delayed ACLR group still had decreased ROM. Gait analysis did not detect meaningful differences between groups at any time point. Surgery, regardless of timing, increased cellularity in the ipsilateral iliac lymph node, but splenic immune cell counts were unchanged.<br /><br />The authors conclude that early ACLR mitigates PTOA development in this mouse model. They suggest that ongoing joint instability and/or persistent hemarthrosis before delayed surgery may contribute to worse cartilage and bone degeneration.

Keywords

anterior cruciate ligament reconstruction

ACLR timing

posttraumatic osteoarthritis

cartilage degeneration

mouse model

delayed surgery

immediate reconstruction

range of motion

bone volume

OARSI scores