A comparison of MRI findings in patients with acute and chronic ACL tears.

This retrospective study compared the magnetic resonance imaging (MRI) findings in 87 patients with acute and chronic anterior cruciate ligament (ACL) tears. Sixty patients had acute tears and 27 had chronic tears. The appearance of the torn ligament was examined on MRI, and associated meniscal and osteochondral injuries were described. All findings were verified at arthroscopy. Acute ACL tears (MRI examination was performed within 6 weeks of injury) were typified by the presence of diffuse (58%) or focal (42%) increased signal within the ligament, whereas chronic ACL tears (MRI examination was performed more than 6 months after injury) usually appeared as either a fragmented ligament (44%) or an intact band of low signal with abnormal orientation (30%). Patients with chronic ACL tears had a higher prevalence of medial meniscal tears (78% versus 40%), articular chondromalacia, and an increased posterior cruciate bow ratio (0.47 versus 0.37) in association with chronic ACL tears. A bone bruise was seen in 68% of acute ACL tears but in no case of chronic ACL tear. On MRI, there are salient differences between acute and chronic ACL tears. Chronic ACL tears are associated with a greater prevalence of meniscal and osteochondral injuries. These findings may have implications for future treatment recommendations.