Are there objective biomechanical symptoms of the knee instability after anterior cruciate ligament injury or it’s reconstruction

BACKGROUND: The instability of the knee joint after a rupture of the anterior cruciate ligament and even after its reconstruction remains a pressing problem. The use of a special functional test with fast walking can be considered as a potential tool for verifying this instability.

AIM: to observe the presence of biomechanical differences in the joint function with and without instability, both before and after the anterior cruciate ligament reconstruction.

METHODS: A biomechanical study of the function of walking at fast speeds, including an electromyographic study, was used. 40 patients were examined, of which 22 underwent reconstruction of the anterior cruciate ligament. The patients were divided into two groups — 33 patients with symptoms of instability, and 7 patients without them; the control group included 20 healthy persons.

RESULTS: The time characteristics of the step cycle did not reveal significant differences between the patient groups and the control group. For the amplitudes of movements in the joints, there were also no significant differences between the patient groups and between the affected and intact sides. The only finding was a significant increase in both amplitudes in the knee joint compared to the control for the intact side in the group with instability. The electromyographic study also did not reveal significant differences.

CONCLUSION: The use of a functional test with fast walking does not allow differentiating the state of instability. Thus, the instability of the knee joint during normal walking, even at a high speed, does not manifest itself in any way. To detect it, it is necessary to develop special provocative tests.