Effects of Knee Flexor and Extensor Strength on Subjective Function and Motor Performance of Knees After Anterior Cruciate Ligament Reconstruction.

Objective To evaluate the effects of knee flexor and extensor strength on the subjective function and motor performance of knees after anterior cruciate ligament reconstruction. Methods A total of 53 patients who underwent anterior cruciate ligament reconstruction in the National Institute of Sports Medicine,General Administration of Sport of China from June 2015 to June 2021 and met the inclusion criteria were enrolled in this study.The patients were followed up time for at least 2 years.An isometric muscle strength test system was used to measure the strength of bilateral quadriceps and hamstring muscles.The patients were grouped according to whether the limb symmetry index (LSI) of peak torque of quadriceps and hamstring muscle reached 85% at an angular velocity of 60°/s.Specifically,26 patients were classified into group A (LSI≥85%) and 27 patients were classified into group B (LSI<85%).The subjective function and motor performance of knees were compared between the two groups. Results In terms of subjective function of knees,the international knee documentation committee (IKDC) score (88.76±9.93 <i>vs.</i> 81.08±12.57,<i>P</i>=0.017) and knee injury and osteoarthritis outcome score (KOOS) (86.27±8.96 <i>vs.</i> 80.22±11.31,<i>P</i>=0.036) were different between groups A and B.There was no significant difference in Lysholm score [95.0 (79.8,100.00) <i>vs.</i> 86.00 (66.00,100.00),<i>P</i>=0.238],ACL return to sports after injury scale score (66.08±22.25 <i>vs.</i> 61.12±23.53,<i>P</i>=0.434),Marx score [6.00 (4.75,7.00) <i>vs.</i> 6.00 (4.00,7.00),<i>P</i>=0.805] or Tegner activity score [8.00 (4.00,12.00) <i>vs.</i> 4.00 (2.00,12.00),<i>P</i>=0.566] between the two groups.In terms of motor performance,the single-leg triple hop LSI (0.92±0.13 <i>vs.</i> 0.81±0.18,<i>P</i>=0.016) and single-leg crossover hop LSI (0.96±0.12 <i>vs.</i> 0.84±0.22,<i>P</i>=0.021) showed significant differences between groups A and B,while there was no significant difference in single-leg hop LSI (0.90±0.18 <i>vs.</i> 0.79±0.25,<i>P</i>=0.116) between the two groups.In addition,there was no statistical significance in proprioception [30°:8.83±4.66 <i>vs.</i> 10.73±4.63,<i>P</i>=0.143;45°:6.94±3.82 <i>vs.</i> 7.66±3.93,<i>P</i>=0.504;60°:4.10 (3.20,4.72) <i>vs.</i> 3.90 (2.30,5.20),<i>P</i>=0.493] or Y-balance test results [anterior LSI:0.98 (0.84,1.02) <i>vs.</i> 0.94 (0.86,0.98),<i>P</i>=0.328;posterolateral LSI:1.00±0.08 <i>vs.</i> 0.97±0.07,<i>P</i>=0.249;posteromedial LSI:1.00 (0.97,1.03) <i>vs.</i> 0.96 (0.93,1.03),<i>P</i>=0.179] between groups A and B. Conclusion The patients with good symmetry of quadriceps and hamstring muscle strength after anterior cruciate ligament reconstruction had better subjective function and movement performance of knees than the patients with poor symmetry,which was mainly reflected in the IKDC score,KOOS,single-leg triple hop,and single-leg crossover hop.