The presence of an intact nerve supply is important in the regeneration of injured tissue in some animals. It has not been determined whether an intact nerve supply is important in ligamentous healing. The authors hypothesize that the nerve supply of a ligament might have a significant effect on its healing. The purpose of this paper was to determine whether injury to the nerve supply of the medial collateral ligament in a rat model results in poor ligament healing (which would suggest that intact nerve supply enhances ligament repair). Clinically, such a finding would demonstrate the importance of avoiding injury to nerve-ligament systems in reparative ligament surgery. Twenty three rats underwent complete bilateral dissection of the major nerves supplying the medial collateral ligament, and each ligament was transected at the level of the tibial tuberosity. The major nerve supplies of the experimental ligaments were destroyed by segmental excision, either distally at the medial articular nerves or proximally at the saphenous nerve, while the control ligament's nerve supplies were left intact. The rats were euthanized at 12 days, and each medial collateral ligament was tested biomechanically using a hydraulic materials testing machine. This time point was chosen because the rat ligament transection site heals rapidly, causing the ligament to avulse from its tibial insertion instead of rupturing at the transection site at later time points. This rat medial collateral ligament injury model has shown statistically significant differences in healing at this time point in numerous experiments evaluating the effects of other variables on ligament healing.(ABSTRACT TRUNCATED AT 250 WORDS)