Development of muscle strength in knee, hip and ankle joints after ACL reconstruction

Introduction: We searched for answers for following questions: How does the knee muscle strength change in dependence of post OP time after the same ACL-rehabilitation's program? Which changes in muscle strength occur in hip and ankle muscles after ACL? Methods: In this study 69 patients with ACL-Reconstruction participated, mean 31 years. The Lysholm- and OAK-scores of all were good respectively very good. 28 patients were 3-6 months post OP (Gr. I), 20 were 6-12 months post OP (Gr. II), 21 was 12-24 months post OP (Gr. II). All patients were tested on the isokinetic Cybex 6000, for dynamic concentric strength and endurance. The evaluation parameters chosen were: max.moment at angle speed of 60degrees/sec and endurance index at 120degrees/sec, Results: The analysis of the max. moment showed significant (P < 0.05) changes in both knee extension and flexion in all groups, in the hip flexors and extensors in group I, and hip flexors in group II and III. In the ankle joint we only found significant changes in the plantarflexors of group I. Looking at the endurance index we observed that many muscle groups of the injured leg presented higher values, however the difference is only significant in the knee flexors and extensors of group I and in the hip flexors of group III. Conclusion: Our study showed strength loss in both knee extensors and knee flexors in all patients who had undergone reconstruction surgery after the same ACL-rehabilitation's program. We can state that there is strength loss in hip and ankle muscles in 3-6 months post OP patients. A reduction of muscle strength at the hip flexor from all patients was seen after 12 months post-OP. It is suggested that the strength loss in the hip flexors could be due to bi-articular muscles surrounding the knee. This results has to be consider on the planning of strength training after ACL injuries.