Purpose To summarise all the up-to-date evidence related to knee osteoarthritis (OA) after revision anterior cruciate ligament (ACL), and to determine the overall average postoperative OA, its progression and its prevalence in each knee compartment after a minimum 4 years, independent from patients’ characteristics and surgical techniques.
Methods A systematic review was performed in PubMed and EMBASE. All the studies that reported knee OA at preoperative status, at final follow-up or both were considered for the meta-analysis. A random-effect meta-analysis was used to obtain the incidence and CIs of postoperative OA, OA progression from preoperative status to final follow-up, and OA prevalence in each compartment. Cut-off values for all OA-grading scales were used to dichotomise the outcomes in a normal knee or knee with OA signs.
Results Overall, 19 studies reported the radiographic outcomes after revision ACL in 776 patients, at a mean pooled follow-up of 5.8 years. Age at surgery was 30.2 years. The overall postoperative OA incidence was 61% (CI 50% to 70%). Progression from a normal knee to OA was reported in 20% (CI 10% to 32%) of the participants. Considering single compartments, OA incidence was 46% (CI 41% to 52%) in the medial compartment, 23% (CI 13% to 36%) in the lateral compartment and 27% (CI 18% to 38%) in the patellofemoral compartment.
Conclusions Knee OA was present in almost 60% of the patients at a mean of 6.2 years follow-up after ACL revision, with an almost double-fold incidence in the medial compartment compared to both lateral compartment and patellofemoral compartment. Progression from normal status to OA status was reported in about 20% of cases. These findings highlight the OA as a concrete problem after revision ACL surgery, which could affect clinical results, sport participation and daily life activities.