The shiny corner of the knee: a sign of meniscal osteochondral unit dysfunction.

Abstract

The purpose of this retrospective study is to describe the MRI findings of the "shiny corner" of the knee (bone marrow lesions at the meniscal-covered portions of the tibial plateau) and to determine its association with compromise of the medial meniscal-osteochondral unit. A retrospective review of 200 knee MRI exams was performed and images were evaluated in consensus by two musculoskeletal radiologists. Presence and location of a shiny-corner lesion was recorded, which was defined as a focal, peripheral hyperintense lesion on fluid-sensitive images at the superior portion of the medial tibial plateau. Meniscal and root ligament abnormalities were recorded, including tearing, degeneration, and extrusion. Sixty exams demonstrated a shiny-corner lesion. Shiny corners involved the medial rim of the medial tibial plateau in 50 cases, only involved the posterior rim in seven cases, and only involved the anterior rim in two cases. Patients with shiny corners were older than patients without shiny corners (mean, 53 years vs. 44 years, p = 0.01). The shiny-corner sign was associated with tears of the medial meniscus, root ligament, and meniscal extrusion (p < 0.001). The presence of a shiny-corner lesion could detect a tear of the medial meniscus or root ligaments with a sensitivity, specificity, positive predictive value, and negative predictive value of 62, 97, 95, and 75%, respectively. Shiny-corner lesions of the knee are associated with tears of the menisci and root ligaments. This observation supports the concept that the menisci protect the underlying covered portions of the tibial plateau.