Apparent absence of the posterior horn of the lateral meniscus with chronic anterior cruciate ligament insufficiency and a medial meniscal ramp lesion: a case report

Introduction Persistent non-visualization of the posterior horn of the lateral meniscus in a knee without previous surgery is rare. Case Presentation A 41-year-old man with obesity presented with chronic right-knee pain and recurrent giving-way eight years after an untreated complete anterior cruciate ligament tear. Examination showed positive Lachman, pivot-shift, anterior drawer, and McMurray tests. Magnetic resonance imaging demonstrated chronic anterior cruciate ligament discontinuity, a medial meniscal ramp lesion, and persistent non-visualization of the lateral meniscus posterior horn, with associated degenerative changes. Management and Outcomes No previous meniscal surgery was reported, and no portal scars or hardware were identified. Arthroscopy had not been performed at the time of reporting; therefore, congenital absence could not be distinguished from severe acquired tissue loss, and postoperative outcomes were unavailable. Conclusion Systematic review of all meniscal segments and arthroscopic confirmation, when clinically indicated, are essential before labeling an absent-appearing meniscal segment as congenital.