The post-arthroscopic knee: fundamental imaging concepts and emerging techniques.

MRI is central to evaluation of the post-operative knee, providing a comprehensive assessment of reconstructions, repairs, and cartilage restoration procedures. Accurate interpretation requires familiarity with operative techniques, graft biology, and the expected temporal evolution of post-operative imaging findings. This review presents a practical, imaging-based approach to contemporary knee surgery. Emphasis is placed on anterior cruciate ligament reconstruction, the renewed interest in primary repair, and common mechanisms of failure. Meniscal surgery, including repair, root repair, centralization, and transplantation, is discussed with attention to expected post-operative MRI appearances and findings suggestive of recurrent or failed repair. Finally, cartilage resurfacing and restoration techniques are reviewed using a systematic framework to assess graft infill, integration, surface congruity, and subchondral bone response. By integrating surgical context with time-dependent MRI findings, this review aims to provide radiologists with a practical framework to distinguish expected post-operative changes from complications, improving diagnostic confidence and clinical relevance of post-operative knee MRI interpretation.