Cyclic loading in knee ligament injuries

The effect of cyclic loading on knee ligaments was studied both in vivo and in vitro. The compliance of the medial collateral ligaments of athletes participating in hockey, basketball, soc cer, and downhill skiing was determined by using a specially built machine. Tests were conducted before and after partici pation in the various sports. Most subjects tested showed an increased compliance after their respective sporting activities. This observation was confirmed in the laboratory by imparting cyclic loading to 10 people under controlled conditions. The in vitro studies were conducted on the medial collateral ligaments of rats. These were tested to determine the effect of cyclic loading on the strength and stiffness of the ligaments. Results show a clear relationship between decreased stiffness or soften ing and a reduction in strength of the ligament. The amount of softening was related to the cyclic stress in the ligament.