OBJECTIVE: LBSA0103 is a recently developed high-molecular-weight, cross-linked, non-animal hyaluronic acid (HA). The safety of LBSA0103 has been investigated only in a limited number of patients, therefore this prospective study was designed. This study sought to assess the safety including injection-site reactions and adverse drug reactions after a single intra-articular injection of LBSA0103 in patients with osteoarthritis (OA) of the knee joint. METHODS: This study was a multicenter, single-arm, prospective cohort study. After screening, eligible patients with OA of the knee joint (Kellgren-Lawrence grades I-III) were enrolled, received a single intra-articular HA (LBSA0103) injection, and were followed up for two weeks. Any adverse events including injection-site reactions and adverse drug reactions were evaluated by the investigators. RESULTS: A total of 1949 subjects (2976 knee joints) was enrolled, all of whom received a single intra-articular injection of LBSA0103. Injection-site reactions occurred in 5.59% of enrolled subjects (109/1949), and the most frequently reported injection-site reaction was pain (4.87%), followed by swelling (1.03%). Most of the injection-site reactions were transient and resolved within 14 days without additional treatment. The incidence of adverse drug reactions other than injection-site reactions was 0.67% (13/1949). Most adverse events were of mild severity. No serious adverse events related to the study drug were reported. CONCLUSIONS: A single intra-articular injection of LBSA0103 in patients with OA of the knee joint was safe, and no significant safety concerns were observed. As such, LBSA0103 could be safely applied as an intra-articular injection for the management of knee OA. TRIAL REGISTRATION: The study was registered at ClinicalTrials.gov (identifier: NCT04369261).