Meniscal translation during knee flexion: what do we really know?

Purpose Translation during knee flexion is a key function of the menisci. The amount of translation displayed by the medial and lateral meniscus during knee flexion, particularly while loadbearing, remains relatively unknown. To address this lack of knowledge, a systematic review of the relevant literature was performed. Methods We performed a literature search for studies in which a primary aim was to report the anterior–posterior translation of the menisci during knee flexion. Data were collected on the characteristics of the sample, the imaging approach, measurement and analysis techniques, and outcome variables. We scored the quality of studies and their reporting using a modified Coleman methodology score with ten criteria, with a maximum possible score of 100. Results Twelve full-text studies were retrieved that met the inclusion criteria. Of these, the in vitro studies ( N = 4) scored the lowest for methodology (median 44.5), with in vivo studies of healthy knees ( N = 4) (median 60) and in vivo comparative studies ( N = 4) scoring highest (median 74.5). The evidence from studies with the highest methodology scores (>65) ( N = 4) indicate that the lateral meniscus translates more posteriorly than the medial meniscus during flexion. In addition, meniscal translation is influenced by loading, particularly in knee rotation, but not by ACL deficiency, despite greater posterior translation of the medial femoral condyle during flexion. Conclusions The generally low methodological quality of studies suggests that caution is required when interpreting meniscal translation during knee flexion reported in the literature. While the methods for assessing meniscal translation in vivo continue to improve and provide opportunity for clinical implementation, there remains a lack of robust evidence regarding meniscal translation in the healthy knee for comparative purposes. A number of recommendations are made for future studies to address key limitations identified in previous investigations. Additional studies of high methodological quality are required to quantify the relationships between joint loading, joint pathology and meniscal translation during knee flexion. Level of evidence III.