Differences in gait and muscle strength of patients with acute and chronic anterior cruciate ligament injury

Background: Anterior cruciate ligament (ACL) injury is one of the most common injuries of the area surrounding the knee. Muscle strength deficiency is observed following an ACL injury. Determining differences in muscle strength and gait between patients with acute and chronic ACL injury will provide crucial information for assessments and treatment plans. Methods: We evaluated 60 patients with ACL rupture. Patients were classified into acute and chronic groups. We compared measurements of anthropometric parameters, muscle strength, gait and functional questionnaire. Findings: The muscle strength of both knee extensors and flexors was higher in the chronic group than in the acute group. The muscle strength index for extensors was 57% in the acute group and 73% in the chronic group. However, the hamstring-to-quadriceps ratio for peak torque of the injured leg in the acute and chronic groups was similarly high at 98% and 101%, respectively. In gait, asymmetry in the hip and knee was observed in the acute group but not in the chronic group. The Knee Injury and Osteoarthritis Outcome Scores (KOOS) for symptoms, pain, activities of daily living, sports and recreational activities were higher in the chronic group than in the acute group. Interpretation: Compared with the acute group, the gait of the chronic group is more symmetrical, and the score of KOOS is also higher. The muscle training protocols could be strategically planned according to these differences. Patients with ACL injury are characterized high hamstrings-to quadriceps peak torque ratio.