Video analysis of anterior cruciate ligament injury: abnormalities in hip and ankle kinematics.

BACKGROUND: Most anterior cruciate ligament research is limited to variables at the knee joint and is performed in the laboratory setting, often with subjects postinjury. There is a paucity of information on the position of the hip and ankle during noncontact anterior cruciate ligament injury.

HYPOTHESIS: When landing after maneuvers, athletes with anterior cruciate ligament injury (subjects) show a more flatfooted profile and more hip flexion than uninjured athletes (controls).

STUDY DESIGN: Case control study; Level of evidence, 3.

METHODS: Data from 29 videos of subjects were compared with data from 27 videos of controls performing similar maneuvers. Joint angles were analyzed in 5 sequential frames in sagittal or coronal planes, starting with initial ground-foot contact. Hip, knee, and ankle joint angles were measured in each sequence in the sagittal plane and hip and knee angles in the coronal plane with computer software. The portion of the foot first touching the ground and the number of sequences required for complete foot-ground contact were assessed. Significance was set at P< .05.

RESULTS: In sagittal views, controls first contacted the ground with the forefoot; subjects had first ground contact with the hind-foot or entirely flatfooted, attained the flatfoot position significantly sooner, had significantly less plantar-flexed ankle angles at initial contact, and had a significantly larger mean hip flexion angle at the first 3 frames. In coronal views, no significant differences in knee abduction (initial contact) or hip abduction angle were found between groups; knee abduction was relatively unchanged in controls but progressed in subjects.

CONCLUSION: Initial ground contact flatfooted or with the hindfoot, knee abduction and increased hip flexion may be risk factors for anterior cruciate ligament injury.