Mechanisms of anterior cruciate ligament injury-induced disruption of joint homeostasis and onset of osteoarthritis.

Osteoarthritis (OA) is a progressive joint disorder that leads to pain and disability for millions of people worldwide. Post-traumatic OA (PTOA), a form of OA, arises secondary to joint injury and often impacts younger individuals. Among the most common joint injuries leading to disrupted joint homeostasis and PTOA is anterior cruciate ligament (ACL) rupture. Even with successful surgical stabilization, the risk of developing PTOA persists due to several factors, including altered biology that contributes to disease progression. Recent research into the biology of ACL injuries has advanced our understanding of the mechanisms by which PTOA develops, including the inflammatory pathways involved, the expression of biomarkers specific to ACL injuries, and their interaction with factors such as the chronicity of the injury. Evidence suggests that homeostatic balance of anabolic and catabolic processes in the knee is disturbed after ACL tears, triggering a catabolic and degenerative phenotype, ultimately leading to premature joint degeneration, pain, and disability. Several key knowledge gaps exist, such as the determinants of the transition from acute to chronic inflammation, inter-patient variability in inflammatory responses, and influence of systemic factors on disease development. PTOA research faces numerous challenges, including protracted nature of the disease, the complexity of joint biology, and difficulties in translating molecular discoveries into clinical practice. Future research should prioritize improving biomarker precision for early detection, developing targeted therapies, and leveraging emerging technologies like machine learning to personalize treatment. This approach will enhance our understanding of the biological basis of PTOA resulting from ACL injuries and identify opportunities to mitigate the long-term consequences of these injuries.