Especially after complex ankle fractures, patients regularly suffer from residual symptoms, presumably due to occult intra-articular injuries. The aim of this study was to evaluate the intra-articular lesions, identify fractures specifically at risk for these, and assess the results after arthroscopically assisted open reduction and internal fixation of complex ankle fractures after 1 year. The primary outcome was the American Orthopedic Foot and Ankle Society (AOFAS) hindfoot score. Secondary outcome parameters were the Olerud and Molander Ankle Score (OMAS), Tegner activity scale, arthroscopic findings, functional assessment, and complications. Thirty-two patients (56% female) were enrolled. Chondral lesions were detected in 91%. Full-thickness lesions treated by microfracturing were observed in 0% of unimalleolar, 43% of bimalleolar, and 40% of trimalleolar fractures. After 1 year, the median (interquartile range) AOFAS was 94 (9) and OMAS was 90 (10) for all patients. When analyzing factors possibly influencing the outcome, age, sex, smoking, grading for surgical procedures according to the American Society of Anesthesiologists, fracture type (uni-, bi-, or trimalleolar), severity of chondral lesions graded according to the International Cartilage Repair Society (grade <4 versus grade 4), and syndesmotic instability had no significant influence on the outcome. The only variable significantly influencing the AOFAS (p = .004) and OMAS (p < .001) was body mass index (BMI; rs = –0.522 and –0.606, respectively), with a higher BMI resulting in inferior outcome scores. Complications were observed in 3 patients, 2 with superficial skin necrosis at the posterolateral incision and 1 nonunion of the medial malleolus. Taken together, these data show that intra-articular injuries were common in ankle fractures. Bi- and trimalleolar fractures were particularly at risk for full-thickness lesions. A higher BMI tended to result in inferior outcome scores. Arthroscopically assisted open reduction and internal fixation led to good to excellent results in all but 1 patient.