Tears of Anterior Cruciate Ligament and Associated Injury in the Knee Joint: MR Imaging

ABSTRACT

PURPOSE: The objective of the study was to evaluate the characteristic findings in tears of the anterior cruciate ligament(ACL) and associated injury at MR imaging. MATERIALS AND METHODS: We reviewed the findings of MR images and the corresponding arthroscopic results of 32 patients with ACL tears. we evaluated the signal intensity and contour of ACL surrounding bony structures, menisci and associated injury of the knee joint. RESULTS: Complete ACL tears were present in 25 patients and partial ACL tears were in 7 patients. Complete ACL tears showed heterogenously increased signal intensity with contour bulging of the ACL in 14 patients (56%) and without bulging or absence in 11 patients(44%). Most patients torn ACL with contour bulging(12/14) had bone bruise, but only one patient torn ACL without bulging contour had bone bruise. ACL with thin continuous low signal band surrounding heterogenously increased signal intensity suggests partial tear, which was seen in three patients of seven proved partial ACL tears. Combined bone injury in ACL tear were in 23 patients (73%) and most of these(22/23) were at midportion of lateral notch of femur and/or posterior portion of lateral tibial plateu. Deepening of lateral notch of femur were noted in 17 patients(53%). Associated injuries of the other ligaments of knee joint were buckling of the posterior cruciate ligament(16/32, 50%) and tears of the medial collateral ligament(11/32, 34%). Posterior horns of menisci were more frequent site of combined injury within menisci in patients with ACL tear. CONCLUSION: Acute tearing of ACL in MRI is seen as heterogenously increased signal intensity with contour bulging of ACL and combined bone bruises. Patients with torn ACL frequently have various combined injury. In patient with knee injury, these associated or ancillary findings suggest that ACL tear is present.