Aim: The aim of the study was to evaluate the effects that an anterior cruciate ligament (ACL) injury of the knee has on postural control and activity of neck, head and trunk muscles in order to investigate the existence of connections between the masticatory system and body posture.
Methods: Surface electromyographic (sEMG) activity of the muscles and their asymmetry index, at mandibular rest position, and during maximal voluntary clenching (MVC), and posturometric and stabilometric measurements of 25 patients (mean age 28+/-9 years) having undergone ACL injury of the left knee were compared with a control non-pathologic group.
Results: At rest, the patients showed a higher sEMG activity of the anterior temporalis, masseter, sternocleidomastoid and lower trapezius, compared with the control subjects (P<0.05). At MVC, the patients showed a lower sEMG activity of the right anterior temporalis and masseter and a higher sEMG activity of the lower trapezius, compared with the control subjects. For the stabilometric measurements, all the subjects showed a significant reduction in the Center of Pressure (CoP) path length during the test with eyes open and cotton rolls, compared with the test with eyes closed and mandibular rest position (P<0.05). In addition, the patients showed a significant displacement of the CoP in a forward direction (P<0.05) and to the righ side (P<0.05), compared with the control-subjects during each test.
Conclusions: ACL injury appears to be associated to a change in the sEMG activity of head, neck and trunk muscles and to a change in the position of the CoP of the body. Cotton rolls seem to improve the stability of the subject.