Anterior cruciate ligament tear
Athletic patient with sudden knee swelling after twisting.
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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.
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.
The indirect signs of a partial ACL tear are the same as for a complete ACL tear, but are typically more subtle. Indirect signs of an ACL injury include pivot-shift bone bruises and fractures of the lateral femoral condyle and posterolateral tibia, “contrecoup” bone bruises in the posteromedial tibial plateau near the semimembranosus insertion, anterior displacement of the tibia, Segond fracture, avulsion fracture of the fibula, lateral meniscal tears at the junction of the posterior meniscofemoral ligament , and buckling of the PCL.
Partial tears of the ACL are a common injury. A significant percentage of partial tears will progress to a functionally complete ACL tear. MRI helps guide the treatment decision process by demonstrating the extent of the ACL injury and by demonstrating co-existing injuries of the ligaments, menisci, articular cartilage and capsule.
- 1. Lintner DM, Kamaric E, Moseley JB, Noble PC. Partial tears of the anterior cruciate ligament. Are they clinically detectable?. (1995) The American journal of sports medicine. 23 (1): 111-8. doi:10.1177/036354659502300119 - Pubmed
- 2. Noyes FR, Mooar LA, Moorman CT, McGinniss GH. Partial tears of the anterior cruciate ligament. Progression to complete ligament deficiency. (1989) The Journal of bone and joint surgery. British volume. 71 (5): 825-33. Pubmed