The purpose of this study is to determine the safety, tolerability, and activity of ICM-203, a recombinant adeno-associated viral (AAV) vector that expresses a therapeutic gene that promotes cartilage formation, reduces joint inflammation and pain, as well as improves joint physical function, by injecting escalating doses of ICM-203 into the knee of subjects with mild to moderate knee osteoarthritis (OA). Approximately 6 to 18 subjects will be enrolled into 3 successive dose-escalating groups in a 3+3 study design, whereby 3 study subjects in each group will be dosed sequentially with ICM-203 and 3 additional subjects will be dosed at the same dose level if a dose limiting toxicity (DLT) occurs in any of the first 3 subjects.