Biological impact of meniscus injury on post-traumatic osteoarthritis.

Post-traumatic osteoarthritis (PTOA) is a common and debilitating problem following meniscal injury, which may lead to pain, loss of function, and early joint failure. Over the past 25 years, clinical, laboratory, and translational studies have greatly improved our understanding of PTOA pathogenesis and prevention. Clinical studies have established the benefit of meniscal preservation in preventing PTOA, leading to a significant increase in meniscus repair. Similarly, improved understanding of the biomechanical importance of the meniscal root attachment has increased focus on the detection and treatment of meniscal root injuries. Laboratory studies have demonstrated a preliminary mechanistic pathway of PTOA development following meniscal injury, whereby injury and altered joint loading stimulate a pro-inflammatory response that leads to both articular cartilage breakdown and impaired meniscal healing. In vitro evidence suggests that mechanical loading of the meniscus may ameliorate this catabolic response, with implications for treatment and rehabilitation protocols. Numerous animal models have emerged, allowing for in vivo assessment of PTOA initiation and offering a platform to test potential therapeutic targets. Despite these advances, meniscal repair remains imperfect and is not always possible, and investigations translating laboratory findings to the human setting have been limited. Future directions include further characterizing the immune and cellular responses to meniscal injury, investigating therapies to target the pro-inflammatory cascade and enhance meniscal healing, and developing new models to better distinguish PTOA pathogenesis in human subjects. Continued laboratory, translational, and clinical research efforts are required to identify treatment strategies to reduce the burden of PTOA after meniscal injury.