It has been proposed that intraoral devices can influence cervical posture. Cervical posture might also be influenced by stimuli from the lower limbs, such as injury of the knee. The hypothesis to be tested is that intraoral devices are useful during the rehabilitation of orthopedic patients to accelerate the restoration of postural control. This study evaluates cervical posture on lateral skull radiographs in subjects who suffered anterior cruciate ligament (ACL) injury of the left knee. Twenty adult Caucasian males (mean age 30.6+/-9.2 yrs.) with ACL injury of the left knee were compared with 40 control subjects (mean age 27.9+/-7.2) who did not show any ACL injury. Lateral skull radiographs, made in natural head position (mirror position), were obtained for all subiects. Various postural and morphological variables were individualized on each radiograph. To assess errors due to landmark identification, duplicate measurements were made of 15 radiographs and compared using the Dahlberg formula. The method error from both sources was less than 0.5 degrees for all angular measurements and less than 0.5 mm for all linear measurements. No difference was observed between the two groups in any of the morphological variables of face or in the cervical lordosis angle (CVT/EVT). However, subjects in the study group showed significantly higher craniocervical angulations (SN/OPT, SN/CVT, SN/EVT, pns-ans/OPT, pns-ans/CVT, pns-ans/EVT, GoGn/OPT, GoGn/CVT, GoGn/EVT) compared with the control subjects (p<0.001). The subjects with ACL injury had significant head extension compared with the control subjects.