Fig. 1.

Principles of local gene therapy for the treatment of orthopaedic conditions. The therapeutic gene, usually in its cDNA form, is incorporated into a viral or non-viral vector and delivered to a site of disease or damage in an in vivo or ex vivo fashion. For in vivo delivery, the vector is administered directly to the relevant site. For ex vivo delivery, the vector transfers genes to cells outside the body, and the genetically modified cells are then administered to the relevant site.