Magnetic resonance imaging findings in chronic anterior cruciate ligament‐deficient knees: A systematic review of meniscal, cartilage, tibial translation and ligamentous changes

Abstract Purpose The purpose of this study is to systematically review the literature for time‐dependent changes in knee anatomy and morphology on magnetic resonance imaging (MRI) in patients with chronically deficient anterior cruciate ligament (ACL) knees. Methods Four databases were searched from inception until 19 January 2025, for primary research studies (level of evidence: II–IV) reporting MRI findings in chronically (defined as >6 months) ACL‐deficient patients. Data regarding time from injury to MRI, sample size, demographics (age, biological sex), comparison group, and MRI findings (meniscal tears, cartilage injuries, posterior cruciate ligament [PCL] angles, collateral injuries, anterior tibial subluxation) were abstracted; cohort studies with acute ACL tear groups were included for pooled comparison. Data were presented narratively and pooled for statistical analysis when possible. Results From the 22 studies selected, 2863 patients were included, mean age was 27.9 years (range: 22.6–35.0, ±2.91 years), and 1957 were males (68.3%). A total of 1360 patients had chronically deficient ACL knees (>6 months from injury). The weighted mean time from injury to MRI was 27.2 months (range: 12.8–66.0 months, 11 studies). Compared to acute ACL‐injured knees, chronic anterior cruciate ligament deficiency (ACLD) patients had a higher rate of medial meniscus injuries (50.3% vs. 36.0%, p < 0.001), medial femoral condyle lesions, medial tibial plateau cartilage lesions, and anterior medial tibial subluxation (+1.6 mm, p < 0.001). The incidence of medial meniscus injuries increased linearly over time. Pooled analysis showed no differences between acute and chronic ACLD knees for lateral meniscus injuries or anterior lateral tibial subluxation. Chronic ACL‐deficient knees demonstrated greater PCL buckling, anterolateral ligament attenuation, ACL fragmentation, alongside reduced bone bruising and joint effusion. Conclusions This systematic review found a higher rate of medial meniscus injuries, medial femoral condyle and medial tibial plateau cartilage lesions, anterior medial tibial subluxation, PCL verticality and ALL and ACL attenuation in chronic ACL‐deficient knees. Level of Evidence Level II–IV, systematic review.