A study of the mechanisms influencing ligament growth

This study investigated the effects of tension and/or exogenous growth hormone on the growth (elongation) of ligaments. In the first experiment, tension was applied to the lateral collateral ligaments of immature rabbits. In the second experiment, a group of skeletally mature rabbits was given exogenous growth hormone while tension was applied to their lateral collateral ligaments. The results revealed that immature rabbit ligaments elongated 140 +/- 18% when tension was applied, while "control" ligaments elongated 79 +/- 5% (P less than .01). In mature rabbits receiving exogenous growth hormone, no significant change was found in the ligament's length with or without the application of tension when compared with controls. Tension applied to ligaments in immature rabbits can increase ligament growth, indicating that physical forces (tension) may be important in the regulation of ligament growth. The same tension applied to mature rabbit ligaments in combination with exogenous growth hormone did not cause a resumption of growth, indicating that tension and the presence of growth hormone are not the only factors necessary for ligament growth.