09/02/2026
Did you know ACL injuries can heal? Surgery is not always needed.
📘 In a brand-new longitudinal, pragmatic cohort study (NACOX), Kvist and colleagues (https://www.jospt.org/doi/10.2519/jospt.2026.13397) investigated whether the anterior cruciate ligament (ACL) shows measurable structural “recovery” on high-resolution MRI during the first two years after an acute ACL rupture, and whether MRI signs of continuity
🦵 The authors followed 129 patients aged 15–40 years who sustained a primary ACL injury within the previous six weeks and were managed according to routine Swedish practice: structured, supervised rehabilitation as first-line care (immediate weight bearing, no range of motion restrictions, and criteria-based progression through the different phases of rehabilitation) with ACL reconstruction (ACLR) considered later if needed.
🩻 Participants underwent 3-Tesla 3D proton-density fat-saturated MRI at baseline and at 3, 6, 12, and 24 months. ACL morphology was graded using the ACTS system (Continuity, Thickness, Shape), designed to separate true fiber continuity from surrounding synovial or scar tissue; two experienced readers scored scans independently and then reached consensus.
📉 Patient-reported outcomes (e.g., IKDC-SKF), perceived stability, episodes of “giving way,” instrumented anterior laxity (KT-1000), quadriceps strength, and activity level were assessed at follow-ups.
📊 Over 24 months, 47% of participants underwent ACLR. Among those with available MRIs prior to any censoring event (ACLR or a new ACL-affecting injury), nearly half showed evidence of ligament continuity at their last MRI: 48% for overall ACL structure and 43% for fiber continuity. Importantly, ACTS grades improved by at least one step in a substantial proportion of patients across follow-ups (reported range 31%–81%, depending on timepoint and domain).
📊 MRI-defined continuity also mattered clinically. At 24 months, patients with evidence of continuity in overall ACL structure reported fewer giving-way episodes (11% vs 50%), and continuity was associated with lower sagittal laxity at both 12 and 24 months (including fewer patients exceeding a ≥3 mm side-to-side KT-1000 difference). Fiber continuity was additionally linked to better quadriceps strength symmetry at 24 months. In contrast, associations with broader patient-reported outcomes were uncertain, largely because estimates were imprecise (wide confidence intervals).
💡 Taken together, the study challenges the traditional assumption that a ruptured ACL cannot regain structural continuity without reconstruction.
⭕ At the same time, the authors are careful about inference: follow-up at 24 months was limited (n=43), baseline imaging sometimes occurred relatively late after injury, rotational instability was not assessed instrumentally, and early ACLR truncated MRI follow-up for many patients—factors that may blur both the true healing rate and its relationship to symptoms and function.