This study investigated the effect of increased suture material within the flexor tendon repair site on tensile strength in a canine model after in vivo healing. Four-strand modified Savage suture repairs with the knots located either inside or outside the repair site were performed in dogs. The tendons were placed on a passive-motion protocol after surgery and were biomechanically tested at 1, 3, and 6 weeks of in vivo healing. The knots-outside technique initially was 1.14 kg stronger on load-to-failure testing. After 6 weeks of healing, the knots-inside tendons had equal tensile strength (3.91 +/- 0.50 kg [inside] vs 4.16 +/- 0.66 kg [outside]). Relative tensile strength compared to initial strength showed an increase of 20% for the knots-outside technique and an increase of 67% for the knots-inside technique after 6 weeks. Suture material within the repair site did not have any deleterious effects on tensile strength and may stimulate tendon healing.