An Electromyographic Analysis of the Knee During Functional Activities

Abstract

This study compared the electromyographic activity of normal (N = 22), rehabilitated anterior cruciate ligament-deficient (N = 8), and -reconstructed knees (N = 10) while subjects performed activities. Each sub ject had evaluation of 8 muscles during 7 functional ac tivities. Sixty-seven percent of the differences in the quadriceps muscle reflected increased activity in the vastus lateralis muscle of the rehabilitated group; 75% of the differences in the hamstrings muscles noted in creased biceps femoris muscle activity in the rehabili tated group; 56% of the differences in the lower leg mus culature showed increased tibialis anterior muscle activity in the rehabilitated group. Eighty-six percent of the statistically different intervals involved rehabilitated subjects demonstrating increased activity over recon structed or normal subjects or both. The presence of a quadriceps-hamstrings muscles coordinated response was identified consistently in all 3 groups in each ac tivity. This study supports surgical reconstruction for the anterior cruciate ligament-deficient knee. It also dem onstrates the importance of the vastus lateralis, biceps femoris, and tibialis anterior musculature in the reha bilitation of the anterior cruciate ligament-deficient patient. The presence of a quadriceps-hamstrings muscles coordinated response indicates that mechano receptors mediating this reflex arc exist in structures other than the cruciate ligament.