Gene therapy is a technique that may offer advantages over current methods of cytokine delivery to ligaments. To determine if implanted genes could be expressed in normal and injured knee ligaments, the medial collateral ligament and anterior cruciate ligament wcrc studied in 18 rabbits. A retroviral rx vivo technique using allograft medial collateral ligament and anterior cruciate ligament fibroblasts aud an adenoviral in vivo technique were compared as methods for delivering the LacZ marker gene to knee ligaments. Bilateral knee surgeries were performed, and the rabbits were equally divided into three groups. Group 1 received the retrovirus and the medial collateral ligament was ruptured, Group 2 received the adenovirus and the medial collateral ligament was ruptured. and Group 3 received the adenovirus and the medial collateral ligament was not injured. The anterior cruciate ligament was not injured in any group. The medial collateral and anterior cruciate ligaments of the right knees received loh allografted, transduced ligament fibroblasts or lo9 adenovirus particles, whereas the ligaments of the left knee received a similar volume of saline solution only. Equal numbers of rabbits were killed at 10 days. 3 weeks, and 6 weeks following the procedure. Ligament samples were stained with X-gal to detect the expression of the LacZ gene product, P-galactosidase. LacZ gcnc expression was cvidcnl in ruptured and uninjured medial collateral ligaments as well as in the anterior cruciate ligament. The expression lasted between 10 days and 3 weeks in the medial collateral and anterior cruciatc ligaments with use of the retrovirus and between 3 and 6 weeks in the medial collateral ligament and at least 6 wceks in the anterior cruciatc ligament with thc adenovirus. The length of gene expression in the ruptured and uninjured medial collateral ligaments did not differ. These preliminary studies indicate that gene transfer to normal and injured knee ligaments is possible.