Isokinetic thigh muscle performance after long-term recovery from patellar dislocation.

Eighty-two patients (50 women, 32 men) underwent isokinetic muscle testing on average 13 years after a conservatively treated unilateral primary patellar dislocation. Three study groups were formed according to the natural history of recovery: group A (n = 32), patients with only primary conservative treatment; group B (n = 34) patients with conservative (group B1; n = 24) or surgical (group B2; n = 10) treatment of redislocations; group C (n = 16) patients with other residual complaints (anterior knee, pain subluxations) requiring surgery. The Cybex 6000 dynamometer system was used as the testing machine for quadriceps and hamstrings muscles, with proportional deficits of peak torque as the test parameter. Isokinetic testing revealed both quadriceps and hamstring muscle atrophy even after long-term recovery from injury. There were statistically significant differences between the three study groups at both tested speeds of quadriceps muscles (60 rad/s, P < 0.002; 180 rad/s, P < 0.009). Groups B1 and B2 presented similar results. The muscle performance findings are probably due to more than one factor: primary immobilization, poor outcome, patellofemoral degeneration, redislocations, and residual knee complaints followed by surgery and deficiency in motor control of thigh muscle had--together or separately--an effect on muscle performance.