Hidden lesions of the posterior horn of the medial meniscus: A systematic arthroscopic exploration of the concealed portion of the knee

Background: Anterior cruciate ligament (ACL) tears are frequently associated with meniscal lesions. Despite improvements in meniscal repair techniques, failure rates remain significant, especially for the posterior horn of the medial meniscus. Purpose: To determine whether a systematic arthroscopic exploration of the posterior horn of the medial meniscus with an additional posteromedial portal is useful to identify otherwise unrecognized lesions. Study Design: Case series; Level of evidence, 4. Methods: In a consecutive series of 302 ACL reconstructions, a systematic arthroscopic exploration of the posterior horn of the medial meniscus was performed. The first stage of the exploration was achieved through anterior visualization via a standard anterolateral portal. In the second stage, the posterior horn of the medial meniscus was visualized posteriorly via the anterolateral portal with the scope positioned deep in the notch. In the third stage, the posterior horn was probed through an additional posteromedial portal. A x2 test and logistic regression analysis were performed to determine if the time from injury to surgery was associated with the meniscal tear pattern. Results: A medial meniscal tear was diagnosed in 125 of the 302 patients (41.4%). Seventy-five lesions (60%) located in the meniscal body were diagnosed at the first stage of the arthroscopic exploration. Fifty lesions located in the ramp area were diagnosed: 29 (23.2%) at the second stage and 21 lesions (16.8%) at the third stage after minimal debridement of the superficial soft tissue layer. The latter type of lesion is called a "hidden lesion." Altogether, the prevalence of ramp lesions in this population was 40%. Meniscal body lesions (odds ratio, 2.6; 95% confidence interval, 1.18-5.18; P < .02) were found to be significantly correlated with a longer delay between injury and surgery. Conclusion: Posterior visualization and posteromedial probing of the posterior horn of the medial meniscus can help in discovering a higher rate of lesions that could be easily missed through a standard anterior exploration. In numerous cases, these lesions were "hidden" under a membrane-like tissue and were discovered after minimal debridement through a posteromedial portal.