The AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Fourth Edition, provides methods to rate knee injuries treated by partial or total menisectomy and also provides methods to rate knee injuries treated by partial or total menisectomy. Although accompanying tables permit impairment rating of most knee injuries, arthroscopy and new surgical procedures have permitted early diagnosis of osteochondral fracture defects that are not easily rated. A peripheral meniscal tear in the fascular part of the meniscus potentially is repairable, but impairment rating after treatment is challenging. If the only surgical procedure was meniscal transplantation and if preoperative radiographs demonstrate joint space narrowing that is sufficiently significant to rate as an impairment, the knee probably can be rated using the joint space narrowing measurement and Table 62. The AMA Guides is silent about rating the impairment when an osteochondral fracture has occurred. If, after time for healing and rehabilitation, the joint has limited motion, atrophy in supporting muscles, or joint space narrowing on radiographs, the rating for those problems probably will adequately describe the impairment. Long-term results of operations that attempt to repair the meniscal or articular cartilage are not known, and impairment rating after one of these procedures may change with time and the publication of additional studies.