Sagittal plane knee translation and electromyographic activity during closed and open kinetic chain exercises in anterior cruciate ligament-deficientpatients and control subjects

Using electrogoniometry and electromyography, we measured tibial translatio n and muscle activation in 12 patients with unilateral anterior cruciate li gament injury and in 12 control subjects. Measurements were made during an active extension exercise with 0-, 4-, and 8-kg weights and during squats o n two legs and on one leg where the projection of the center of gravity was placed over, behind, and in front the feet. In the uninjured subjects, tib ial translation increased with increasing load except during the squat with the center of gravity behind the feet, which produced the smallest transla tion. For the active extension exercises, translation was greater during ec centric activity. In the anterior cruciate ligament-injured knees, all squa ts resulted in similar translation, which was smaller than that during the active extension exercise. The highest muscle activation was seen during sq uats. Hamstring muscle activity was low. Increased static laxity in the ant erior cruciate ligament-deficient knee can be controlled during closed but not during open kinetic chain exercises. Coactivation of the quadriceps and gastrocnemius muscles seems to be important for knee stability, whereas ha mstring muscle coactivation was insignificant. To minimize sagittal transla tion during nonoperative management of anterior cruciate ligament-deficient knees, closed kinetic chain exercises are preferable to open kinetic chain exercises, and importance should be attached to the spontaneous coactivati on of the quadriceps and gastrocnemius muscles.