Correlation of magnetic resonance imaging findings with the chronicity of an anterior cruciate ligament tear

Background: Although several findings on magnetic resonance imaging have been demonstrated after anterior cruciate ligament injury, sequential changes on magnetic resonance imaging have not been comprehensively studied. We undertook to correlate four specific findings on magnetic resonance imaging of an anterior cruciate ligament injury over time. Methods: One hundred and forty-five patients with a complete tear of the anterior cruciate ligament confirmed by arthroscopy were divided, according to the time from the injury to the acquisition of the magnetic resonance image, into four groups: acute (within six weeks), subacute (more than six weeks to three months), intermediate (more than three months to one year), and chronic (more than one year). Four findings (anterior cruciate ligament morphology, joint effusion, posterior cruciate ligament angle, and bone bruise) were evaluated for each study group. Results: Strong correlations were found between the magnetic resonance imaging findings and the chronicity of the anterior cruciate ligament tear. Anterior cruciate morphology showed sequential changes with time (p < 0.001). Joint effusion decreased with time, with a significant difference occurring between the acute and subacute groups at six weeks (p < 0.001). The posterior cruciate ligament angle decreased gradually over time (p < 0.001). Finally, the signal contrast of bone-bruising decreased with time, with a significant change occurring after three months (p = 0.049). Conclusions: Our study confirmed that these four magnetic resonance imaging variables are closely correlated with the chronicity of an anterior cruciate ligament tear, and estimation of the chronicity of the tear can be facilitated by an integrative interpretation of these findings. Level of Evidence: Diagnostic Level II. See Instructions to Authors for a complete description of levels of evidence.