GAIT ADAPTATIONS BEFORE AND AFTER ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION SURGERY

Gait analyses of rehabilitated individuals with anterior cruciate liga ment (ACL) deficiency and reconstruction have identified the final ada ptations of increased hip extensor torque and hamstring electromyograp hy (EMG) and decreased knee extensor torque and quadriceps EMG during stance. The initial adaptations to injury and surgery are, however, un known as are the factors that influence the development of the adaptat ions. Identification of the initial response to injury would provide a basis for determining whether the final adaptations are learned autom atically or if they are the result of a lengthy training period in whi ch various factors may affect their development. The purpose of the st udy was to evaluate the initial effects of ACL injury and reconstructi on surgery on joint kinematics, kinetics, and energetics during walkin g. Injured limbs from nine subjects with ACL injury were tested 2 wk a fter injury, and 3 and 5 wk after surgery. Ten healthy subjects were t ested. Kinematic and ground reaction data were collected and combined with inverse dynamics to calculate the joint torques and powers. A kne e extensor torque throughout most of stance was observed in the injure d limbs at all test sessions. This result was in conflict with previou s observations of reduced extensor torque or a flexor torque in rehabi litated patients with ACL reconstruction and patients with ACL deficie ncy. This result also differed from the typical midstance extensor the n flexor torque in healthy control subjects. Trend analysis showed a s ignificant (P < 0.001) change in average position at the hip and knee, extensor angular impulse at the hip, and positive work done at the hi p 3 wk after surgery followed by a partial rehabilitaton at 5 wk after surgery. Power and work produced at the knee were reduced fivefold (P < 0.001) after 5 wk of rehabilitation and did not recover to pre-surg ical levels. The existence of a long-lasting knee extensor torque 2 wk after injury indicated that the adaptation process to ACL deficiency is lengthy, requiring many gait cycles, and that numerous factors coul d be involved in learning the adaptations.