Objective To explore the impact of varying meniscal injury types on the optimal timing and effectiveness of

arthroscopic surgical intervention. Methods A retrospective analysis was conducted on 160 patients with varying types of

meniscal injuries， who were admitted to our hospital between March 2022 and March 2024. These patients were stratified into

ten distinct groups， with 16 patients in each， based on the nature of their meniscal injury （horizontal fissure， longitudinal

tear， radial tear， discoid tear， mixed tear） and the elapsed time from injury to surgical intervention （early vs. late）.

Specifically， the groups were labeled as follows： A （horizontal fissure-early）， B （horizontal fissure-late）， C （longitudinal tear-early）， D （longitudinal tear-late）， E （radial tear-early）， F （radial tear-late）， G （discoid tear-early）， H （discoid tear-late）， I （mixed tear-early）， and J （mixed tear-late）. The study compared key outcome metrics across multiple preand post-operative time points （postoperative day，1 month，3 months，6 months， and 9 months）， including the International Knee Documentation Committee （IKDC） score， Lysholm knee score， visual analog scale （VAS） pain intensity，inflammatory biomarker fluctuations， knee range of motion （ROM）， the proportion of excellent knee function outcomes， and the frequency of postoperative complications. To assess the effectiveness of arthroscopic surgery timing， a difference-indifferences （DID） analytical approach was employed. Results The postoperative evaluations at 1，3，6， and 9 months revealed a steady enhancement in IKDC and Lysholm scores， surpassing preoperative baselines （P<0.05）. Notably， the early surgical intervention cohort demonstrated superior outcomes compared to the late group， with groups C and D particularly outperforming their contemporaneous counterparts （P<0.05）. Regarding pain intensity， as measured by the VAS， there was a consistent reduction from preoperative levels （P<0.05）. Again， the early group reported lower pain scores than the late group， and Groups C and D exhibited the mast notable decrease among all groups simultaneously （P<0.05）. The knee range of motion （ROM） progressively increased from preoperative to postoperative assessments at 1，3，6， and 9 months （P< 0.05）， with the early group displaying greater gains than the late group （P<0.05）. Additionally， inflammatory markers like interleukin-1β（IL-1β） and tumor necrosis factor alpha （TNF- α） exhibited a gradual decline post-surgery compared to preoperative levels （P<0.05）， with the early group and groups C and D demonstrating the most significant reductions （P<0.05）. In terms of knee function， the early group had a higher overall excellent and good rate compared to the late group （P<0.05）. Notably， group C achieved the highest rate of 93.75%， while group B had the lowest at 62.50%. Furthermore， the incidence of postoperative complications was lower in the early group （P<0.05）， with group C exhibiting the lowest rate of 6.25% and group B the highest at 31.25%. The difference-in-differences （DID） analysis underscored the benefits of early surgery， with the early group demonstrating a more pronounced improvement in IKDC （β=1.869，P<0.001） and Lysholm （β= 3.216，P<0.001） scores， as well as a more substantial reduction in VAS scores （β=-1.248，P<0.001） compared to the late group. Conclusion The early surgical intervention cohort demonstrated superior IKDC and Lysholm scores in comparison to the late group， whereas the VAS scores were less favorable in the early group as opposed to the late group. Additionally， the

Different types of injuries, Meniscus injuries, Arthroscopic surgery, Timing of surgery