Purpose: To analyze and compare clinical outcomes after anterior cruciate ligament (ACL) reconstruction 5 and 10 years postsurgery between patients with concomitant intra-articular injuries and those with isolated ACL injury at reconstruction. Methods: Registrations were made using a web-based protocol by physicians for baseline and surgical data. Patients registered their Knee Injury and Osteoarthritis Outcome Score (KOOS) preoperatively and at 5 and 10 years postsurgery. The exclusion criteria for the present study were revisions of previously unregistered ACL surgeries, non-ACL surgeries, patients for whom 10-year follow-up data had not yet been collected, and the proportion of index surgeries that were revision or contralateral interventions. Results: There were 1,295 KOOS scores available for patients 5 years postsurgery, and 1,023 10 years postsurgery from a baseline of 2,751 index reconstructions. A deterioration between the 5-and 10-year scores was observed for patients with concomitant meniscus injury on the KOOS subscales for pain (P = .015), symptoms (P = .005), sport and recreation (P = .011), and knee-related quality of life (QoL) (P = .03) compared with patients with isolated ACL injury. Correspondingly, KOOS subscale score deterioration was seen for combined concomitant cartilage and meniscus injuries for pain (P = .005), symptoms (P = .009), sport and recreation (P = .006), and QoL (P amp;lt; .001). The largest deteriorations were found in sport and recreation (-5.9 points; confidence interval [CI] -10.1, -1.1) and QoL (-6.5 points; CI -10.3, -2.8) subscale scores for patients with concomitant meniscal and cartilage injuries. A similar pattern was not seen between patients with concomitant cartilage injury and isolated ACL injury. Conclusions: The present study reveals that concomitant meniscus injuries at the index operation, either in isolation or in combination with cartilage lesions, render a deterioration of scores on the KOOS outcome subscales for pain, sport and recreation, and quality of life between 5-and 10-year postsurgery follow-up of ACL-reconstructed patients. No such deterioration was seen for patients who had isolated ACL injury.