Presentation
Athletic patient with sudden knee swelling after twisting.
Patient Data
The ACL presented fuzzy outline with areas of intermediate signal intensity in all pulse sequences within its substance, yet its fibers are seen stretched with no evidence of complete tear or retraction.
Normal MRI appearance of both menisci, PCL, collateral and patellar retinacular ligaments as well as the quadriceps and infrapatellar tendons.
Mild intra-articular joint effusion is noted.
Mild tibial plateau and lateral femoral epicondyle bone marrow edema.
Intact peri-articular musculature with preserved intervening fat planes.
Case Discussion
This case demonstrates typical partial intrasubstance ACL tear with moderate knee effusion. Diagnosis of ACL tear is made by detection of primary and secondary signs. Primary sign includes discontinuity and abnormal signal of ACL fibers and secondary signs include PCL buckling, anterior tibial translation, uncovered PHLM, empty notch sign, bone bruise and Segond fracture.