Introduction Discoid medial meniscus is extremely rare, although dis- coid lateral meniscus is not uncommon [6]. Bilateral dis- coid medial menisci are even less common; only 11 cases have been reported since Cave and Staples [2] reported first undisputed discoid medial meniscus in 1941 [3, 4, 5, 8, 11, 13, 14]. Six of these patients underwent magnetic resonance imaging (MRI) of their knees [2, 3, 4, 8, 11]. We present another case of bilateral discoid medial menisci with tears and associated osseous changes in the adjacent proximal tibia detected by MRI and confirmed by arthroscopy. Case report An 18-year-old, male, active, recreational soccer player was first seen with pain and swelling in his left knee. He began to experi- ence vague pain in the medial side of the knee about 1 year before presentation, and this had gradually worsened. After the onset of a limp and subsequent inability to participate in sports he sought medical attention. There was no history of definite trauma. Clinical examination revealed a knee effusion, quadriceps mus- cle atrophy, and medial joint line tenderness. Palpation of the me- dial joint line was painful, and McMurray’s sign was strongly pos- itive during internal rotation. There was no sign of the “snapping knee” during flexion and extension. There was discomfort with flexion, but he could perform full extension and flexion to 130°. He had no evidence of ligamentous laxity or instability and no symptoms related to the patellofemoral joint. Routine blood tests, including erythrocyte sedimentation rate, and blood serology were normal. Radiography revealed increased concavity of the medial tibial plateau in both knees (Fig. 1). The increased depression of the me- dial plateaus (cupping) was more pronounced in the right knee. MRI of the right knee demonstrated that the medial meniscus was discoid with extensive intrasubstance degeneration and horizontal tear and also showed some depression of the medial tibial plateau and decreased signal intensity of the subchondral medial tibial epi- physis consistent with reactive sclerosis (Fig. 2). In arthroscopy of the right knee a complete discoid medial meniscus was found, and no abnormality was apparent on the femoral surface of the meniscus (Fig. 3a). However, there was a midsubstance horizontal cleavage tear, which communicated with the joint cavity through tibial surface of the meniscus (Fig. 3b). Abstract We present here the third case report of bilateral discoid me- dial menisci with associated bone changes. An 18-year-old man had bi- lateral medial tibial plateau depres- sion (cupping) accompanying medial discoid menisci documented by mag- netic resonance imaging and con- firmed by arthroscopy. The patient was treated successfully by excision of the torn central anomalous discoid portion of the menisci using arthro- scopic partial resection technique. Keywords Medial discoid meniscus · Magnetic resonance imaging · Arthroscopy KNEE Knee Surg, Sports Traumatol, Arthrosc (2001) 9 : 217–220 DOI 10.1007/s001670100204 Ö. Ahmet Atay M. Nedim Doral Üstün Aydingöz Gürsel Leblebicioglu Bilateral discoid medial menisci: association with bone changes in the tibia Received: 8 October 2000 Accepted: 15 January 2001 Published online: 30 March 2001 © Springer-Verlag 2001 Ö. A. Atay (✉) · M. N. Doral · G. Leblebicioglu Department of Orthopedics and Traumatology, Hacettepe University Medical Center, 06100 Ankara, Turkey e-mail: oaatay@yahoo.com, Tel.: 90-312-3051793, Fax: 90-312-4683716 Ü. Aydingöz Department of Radiology, Hacettepe University Medical Center, 06100 Ankara, Turkey