Isokinetic torque deficit of the knee extensor muscles in the operated leg was measured in 21 male patients (mean age 26.4 +/- 1.9 years) who had undergone arthroscopic partial medial meniscectomy. The isokinetic torque testing was performed 1, 3, and 6 months postoperatively using the Cybex II dynamometer according to standard technique. Isokinetic knee extension peak torque (PT) at angular velocities of 60 degrees and 180 degrees/s was determined in both legs, and the proportional PT deficit in the operated leg was compared with that in the nonoperated leg. A significant (P<0.001) isokinetic PT deficit in the operated leg in testing with angular velocity of 60 degrees and 80 degrees/s was observed at 1 month (28.6% and 31.0%, respectively) and 3 months (19.8% and 15.8%, respectively) postoperatively. At 6 months postoperatively a significant (P<0.001) isokinetic PT deficit (18.2%) of the knee extensor muscles in the operated leg was observed only in testing with angular velocity of 60 degrees/s; no significant differences (P>0.05) in isokinetic PT between the operated and nonoperated leg in testing with angular velocity of 180 degrees/s was found 6 months postoperatively. Thus in patients with arthroscopic partial meniscectomy the postoperative recovery of isokinetic strength of the knee extensor muscles in the injured leg is closely related to testing velocity, while it is more delayed at low than intermediate angular velocities.