Duration of in vivo transgene expression after a single intra-articular injection of AAV2-CMV-Luc was observed and quantified using bioluminescence imaging to detect luciferase activity. (A) Bioluminescent images of the left knee joint of a representative rat at 14 days, 1 month, 6 months and 1 year after a single intra-articular injection of AAV-CMV-Luc. (B) Median and interquartile range of bioluminescence observed in the left knee joint of all rats in the study over 1-year following intra-articular injection of AAV-CMV-Luc. N=4–8 rats (N=8 at 14 days, N=6 at 1 and 2 months, N=5 at 3 months, and N=4 from 4 months to 1 year). No significant difference was observed between the different time points.