Psychological readiness and return to sports after ACL reconstruction: A meta-analysis of KOOS scale outcomes at one- and two-year follow-up

Background: The Knee Injury and Osteoarthritis Outcome Score (KOOS) is widely used to evaluate functional outcomes after anterior cruciate ligament reconstruction (ACLR). However, there is limited consolidated evidence on subscale-specific recovery trends over time. Objective: To assess the effectiveness of rehabilitation in improving KOOS subscale scores Pain, Symptoms, Activities of Daily Living (ADL), Quality of Life (QoL), and Sport/Recreation (Sport/Rec) at one- and two-year follow-up post-ACLR. Methods: This PRISMA-compliant meta-analysis (PROSPERO: CRD42025646262) used PICOS criteria. Ten studies were selected from PubMed, Web of Science, and Scopus between 2019 and 2025. Methodological quality was assessed using the Newcastle–Ottawa Scale and GRADE. Random-effects models calculated standardized mean differences (SMDs); heterogeneity was assessed with I2 and τ2. Results: Ten studies (n = 6407–6434 per subscale) were analyzed. KOOS QoL showed the greatest improvement (SMD = 0.46; 95 % CI: 0.093 to 0.835; p = 0.0197), followed by Pain (SMD = 0.37; 95 % CI: −0.02 to 0.76; p = 0.063). Symptoms showed a small-to-moderate effect (SMD = 0.44; p = 0.074), while ADL presented limited improvement (SMD = 0.21; p = 0.1015). Sport/Rec scores improved modestly (SMD = 0.37; p = 0.0732), with large individual gains seen in athletes with lower baseline scores. Heterogeneity was substantial across subscales (I2 = 84.3 %–90.9 %). Conclusion: Rehabilitation after ACLR leads to meaningful improvements in KOOS Pain, QoL, and Symptoms scores. Sport/Rec and ADL also improved, especially in long-duration programs. KOOS is a valuable outcome tool and should be integrated with objective return-to-sport criteria for comprehensive assessment.