Aims: The study aimed to present clinical, biometric, radiographic and patient-reported outcomes (PROMs) from a case series of surgeon-selected presentations of ACL injuries that have been treated without operative intervention. This can help inform decision making processes surrounding surgical versus non-surgical management of ACL injuries.
Methods: Patients with a confirmed diagnosis of isolated ACL rupture based on 3T MRI and clinical examination were included. Selection into the non-operative cohort was guided by surgeon recommendation or patient preference. All patients underwent a structured 24 week rehabilitation program modelled on the KANON protocol, delivered by the patients’ chosen physiotherapist and overseen by the treating orthopaedic surgeon. Functional limb testing (including ACL-RSI score) were assessed at 3 and 6 months post-injury. ACL laxity was objectively measured using Dyneelax at baseline, 6 and 12 months. PROMs including IKDC, Lysholm, and Tegner were recorded at baseline, 6 and 12 months, and any recurrent instability event was documented. Baseline and 12 month MRIs were performed to evaluate radiographic healing and ACL tissue appearance using the ACLOAS scoring system. MRI changes from baseline to follow-up were analysed using a validated MRI classification. Non-operative treatment failures (conversion to ACL reconstruction [ACLR]) were recorded and analysed to inform development of a clinical decision making algorithm.
Results: Between January 2022 and March 2026, 149 patients were enrolled in the study. The mean (SD) baseline characteristics of the cohort were: age 40 (13.2), gender 60% female, BMI 25.7 (4.2), and 39% of injured knees were left. Baseline PROMs included: IKDC 50.1 (19.3), Lysholm score 66.2 (24.5) and median Tegner level 3. At 6 months there was no significant side to side difference in quadriceps and hamstring strength (p = 0.08 and 0.45 respectively) and the mean ACL-RSI score was 57.4 (25.3). At 12 months there was a significant absolute displacement difference of 1.49 (1.03) mm in anteroposterior laxity measured with Dyneelax at 200N (p < 0.001), and a small but significant deficit in flexion range of motion compared to the healthy knee (p = 0.02). Improvements were recorded in all 12-month follow-up PROMs: IKDC 83.2 (14.1), Lysholm 90.9 (13.1) and median Tegner level 5. The appearance of ACL tissue at follow up was classified using the ACLOAS system and this was correlated with the baseline MRI findings. Preliminary regression models revealed positive correlations between improvements in PROMs, RTS performance and imaging based healing. At the time of analysis, 14 patients had converted to ACLR, and no baseline characteristics differed between patients who required surgery and those who did not.
Conclusion: Preliminary findings indicate that this subset of ACL-injured patients demonstrated satisfactory improvement in PROMs and RTS function following the non-surgical protocol. These patients also showed favourable structural healing on MRI and small side-to-side laxity difference as measured by Dyneelax. Further data collection is underway to validate and refine the treatment algorithm.
