To evaluate the characteristic changes in muscles of knee joint after meniscal injury and the necessity of preoperative and postoperative isokinetic exercise program, we performed the isokinetic tests of the knee muscles periodically, preoperative state, postoperative 3 months, postoperative 6 months and compared each other.

The results were as followings;

1) In preoperative state, there were about 10% torque dificit in uninvolved knee extensor & flexor muscle and 33% torque deficit in involved knee extensors, and 27.7% torque deficit in involved knee flexors.

2) The recovery rate of extensor muscle power after menisectomy was faster in uninvolved side than involved side. The muscle power of extensor of uninvolved side came up to normal level within 3 months after menisectomy but that of involved side improved slowly and came up to normal level after 6 months postoperatively.

3) The recovery rate of flexor muscle power after menisectomy was also faster in uninvolved side than involved side and the flexor muscle power came up to normal level earlier than extensor muscle power.

4) The muscle imbalance between uninvolved and involved knee was about 22% at preoperative state but increased to 26% at postoperative 3 months, then, decreased to 13% at postoperative 6 months.

5) The hamstring to quadriceps imbalance (H/Q ratio) was 9.3 at preoperative state but increased to 22% at postoperative 3 months then, decreased to 6.6% at postoperative 6 months.

6) Therefore, we think that the isokinetic exercise is essential program in rehabilitation of knee muscles after menisectomy, especially in early postoperative phase.

And we think that, the isokinetic exercise for extensor is more necessary than flexors and the high velocity isokinetic exercise is more useful.