[Medial collateral ligament of the knee and its surroundings: MRI findings of normal and abnormal structures].

Normal and abnormal structures of the medial corner of the knee were evaluated with coronal and axial MR images. MRI revealed 35 medial collateral ligament (MCL) tears and 61 medial meniscus (MM) tears in 200 consecutive examinations. Just under the MCL, little or no fluid retention was identified between the superficial and deep layers of the MCL or between the MM and MCL in normal knees and in cases of MM tears. At the anterior aspect of the MCL, the deep layer merges with the capsule of the suprapatellar bursa, potentially leaving space for fluid retention. Fluid collection posterior to the MCL was demonstrated in a few cases. Fluid retention with edematous swelling just under the MCL was noted in the cases of MCL tears. MM-MCL distances in the cases of normal structure, MM tears and MCL tears were 2.1 mm, 2.7 mm and 4.7 mm, respectively. The deep layer of the MCL, which was enhanced by the presence of joint fluid, was identified in 71% of cases.