Neuromuscular Performance in Normal and Anterior Cruciate Ligament-Deficient Lower Extremities

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Abstract
The neuromuscular function of the lower extremity in 40 normal and 100 anterior cruciate ligament-deficient vol unteers was evaluated by physical examination, KT- 1000 arthrometer measurements, isokinetic strength and endurance testing, subjective functional assess ment, and an anterior tibial translation stress test. A specially designed apparatus delivered an anteriorly di rected step force to the posterior aspect of the leg while anterior tibial translation was monitored and electro myographic signals were recorded at the medial and lateral quadriceps, medial and lateral hamstrings, and gastrocnemius muscles. Testing was done at 30° of knee flexion with the foot fixed to a scale to monitor weightbearing, while the tibia remained unconstrained. Results indicate that muscle timing and recruitment or der in response to anterior tibial translation are affected by anterior cruciate ligament injury. These alterations in muscle performance change with time from injury, cor relate with an individual's physical activity level, affect subjective functional parameters, and are directly re lated to the degree of dynamic anterior tibial laxity seen with stress testing.