Little Agreement Between Preoperative Kellgren-Lawrence Classification and Intraoperative Outerbridge Score in Patients Undergoing Arthroscopic Partial Meniscectomy

Abstract

Purpose: To determine whether there is a correlation between preoperative Kellgren-Lawrence (KL) grade and intraoperative Outerbridge score, which are both tools used to assess knee osteoarthritis.

Methods: Patients undergoing knee arthroscopy and partial meniscectomy procedures with or without chondroplasty between August 2012 and October 2020 were enrolled in this study. Preoperative KL grades were recorded, and Outerbridge scores were obtained intraoperatively for each of the 6 joint surfaces (medial and lateral femoral condyle, medial and lateral tibial plateau, patella, and trochlea). The total Outerbridge score was then calculated by summing the grades for the 6 joint surfaces. The level of agreement between KL grade and Outerbridge score was assessed using Cohen weighted κ values, with 0 to 0.20 indicating no or slight agreement; 0.21 to 0.40, fair agreement; 0.41 to 0.60, moderate agreement; 0.61 to 0.80, substantial agreement; and greater than 0.80, almost perfect agreement.

Results: A total of 468 patients were included in this study (271 women [58%] and 197 men [42%]; mean age, 49 years [standard deviation, 10.35 years]; mean body mass index, 30.5 [standard deviation, 7]). There was slight agreement between KL grade and total Outerbridge score (κ = 0.05), as well as between KL grade and Outerbridge score for individual joint surfaces (κ range, 0.04-0.20). Similar results were found when we individually analyzed female patients (κ range, 0.06-0.22) and male patients (κ range, 0-0.17) and when we compared patients younger than 40 years (κ range, 0.02-0.19) with those aged 40 years or older (κ range, 0.04-0.15).

Conclusions: There is little agreement between the radiographic KL grade and the intraoperative Outerbridge classification system. Thus, the association between radiographic assessments and cartilage health may need to be reconsidered owing to this lack of correlation.

Level of evidence: Level IV, retrospective therapeutic case series.