Ithurburn, Matthew P.

Background: The impact of maturation on lower extremity strength and function after anterior cruciate ligament reconstruction (ACLR) may help guide future studies of age-specific rehabilitation. Hypothesis Pediatric ACLR patients would demonstrate higher thigh strength symmetry and knee-related function at return to sport (RTS) compared with adolescent and young adult participants who underwent traditional ACLR. Study Design: Prospective cohort study. Level of Evidence: Level 2. Methods: A total of 144 young athletes at the time of RTS clearance post-ACLR were classified into 3 maturational groups (pediatric, n = 16 with physeal-sparing ACLR [mean age = 12.3 years; range = 9.2-14.6 years]; adolescent, n = 113 [mean age = 16.5 years; range = 14.1-19.8 years]; young adult, n = 15 [mean age = 22.0 years; range = 20.5-24.9 years]). Quadriceps and hamstring strength were measured using an electromechanical dynamometer. Knee-related function was measured using the International Knee Documentation Committee (IKDC) subjective form and single-leg hop tests. The Limb symmetry Index (LSI) was used in calculations for hop and strength tests. Group differences were compared with Kruskal-Wallis tests and Mann-Whitney U post hoc tests. Proportions of participants meeting literature-recommended RTS criterion cutoffs were compared among the groups using chi-square tests. Results: The pediatric group demonstrated higher quadriceps LSI ( P = 0.01), IKDC scores ( P < 0.01), single-hop LSI ( P < 0.01), and crossover-hop LSI ( P = 0.02) compared with the young adult group. In addition, the pediatric group demonstrated higher IKDC scores ( P < 0.01) and single-hop LSI ( P = 0.02) compared with the adolescent group. The adolescent group demonstrated higher IKDC scores ( P < 0.01), single-hop LSI ( P = 0.02), and crossover-hop LSI ( P = 0.03) compared with the young adult group. The proportions of participants meeting all RTS criterion cutoffs were highest in the pediatric group and lowest in the young adult group ( P = 0.03). Conclusion: Young athletes at RTS clearance after pediatric ACLR demonstrated higher quadriceps strength symmetry and knee-related function than adolescents and young adults after traditional ACLR. Clinical Relevance: These findings demonstrate the need for further study regarding the impact of these group differences on longitudinal outcomes after ACLR, including successful RTS and risk of second ACL injury.

Background: Previous work shows that young athletes after anterior cruciate ligament reconstruction (ACLR) demonstrate single-leg (SL) landing movement asymmetries at the time of return to sport (RTS); however, the effect of movement asymmetries on longitudinal knee-related function after ACLR has not been examined. Hypothesis/Purpose: The purpose of this study was to examine the effect of SL drop-landing movement symmetry at the time of RTS on knee-related function 2 years later in young athletes after ACLR. The first hypothesis was that young athletes who demonstrated SL drop-landing asymmetries at RTS would demonstrate decreased knee function 2 years later compared with those who demonstrated symmetric SL drop-landing mechanics. The second hypothesis was that SL drop-landing movement symmetry at RTS would be associated with knee functional recovery 2 years later. Study Design: Cohort study; Level of evidence, 2. Methods: This study included 48 young athletes who had undergone ACLR and were assessed at the time of RTS (77% female; mean [±SD] age at RTS, 17.6 ± 2.6 years) and followed for 2 years after RTS. Three sagittal-plane landing variables of interest were calculated using 3-dimensional motion analysis during an SL drop-landing task at the time of RTS: knee flexion excursion, peak internal knee extension moment, and peak trunk flexion. The limb symmetry index (LSI) was calculated for each landing variable using the following: LSI = (involved/uninvolved) × 100%. The LSI was used to divide the cohort into symmetric (SYM) and asymmetric (ASYM) groups for each landing variable: knee flexion excursion (SYM: LSI ≥ 90% [n = 23]; ASYM: LSI < 85% [n = 18]), peak internal knee extension moment (SYM: LSI ≥ 90% [n = 19]; ASYM: LSI < 85% [n = 22]), and peak trunk flexion (SYM: LSI ≤ 105% [n = 25]; ASYM: LSI > 115% [n = 19]). At 2 years after RTS, knee-related function was evaluated using the Knee Injury and Osteoarthritis Outcome Score (KOOS), International Knee Documentation Committee (IKDC) subjective knee form, and performance on SL hop tests. Functional recovery was defined based on literature cutoffs for knee-related functional measures. Differences in 2-year function were compared between the symmetry groups using Mann-Whitney U tests because of nonnormality. Logistic regression was used to determine if landing symmetry at the time of RTS would be associated with 2-year knee functional recovery after RTS. Results: The ASYM knee flexion excursion group demonstrated decreased function at 2 years after RTS compared with the SYM group on the KOOS-Pain (ASYM: 93.0 ± 8.2; SYM: 98.4 ± 3.0; P = .008) and the KOOS–Quality of Life (ASYM: 81.6 ± 16.1; SYM: 94.1 ± 9.7; P = .008). Knee flexion excursion was associated with knee functional recovery on the KOOS-Pain and the KOOS–Quality of Life ( P = .033 and P = .012, respectively) at 2 years after RTS, after controlling for the quadriceps strength LSI and graft type. Conclusion: Young athletes after ACLR with asymmetries in knee kinematics at the time of RTS reported decreased self-reported function 2 years later; however, the clinical importance of these differences needs to be further understood.

Background: Anterior cruciate ligament reconstruction (ACLR) using a hamstring tendon autograft often results in hamstring muscle strength asymmetry. However, the effect of hamstring muscle strength asymmetry on knee mechanics has not been reported. Hypothesis: Participants with hamstring strength asymmetry would demonstrate altered involved limb knee mechanics during walking and jogging compared with those with more symmetric hamstring strength at least 2 years after ACLR with a hamstring tendon autograft. Study Design: Controlled laboratory study. Methods: There were a total of 45 participants at least 2 years after ACLR (22 male, 23 female; mean time after ACLR, 34.6 months). A limb symmetry index (LSI) was calculated for isometric hamstring strength to subdivide the sample into symmetric hamstring (SH) (LSI ≥90%; n = 18) and asymmetric hamstring (AH) (LSI <85%; n = 18) groups. Involved knee kinematic and kinetic data were collected using 3-dimensional motion analysis during gait and jogging. Peak sagittal-, frontal-, and transverse-plane knee angles and sagittal-plane knee moments and knee powers were calculated. Independent-samples t tests and analyses of covariance were used to compare involved knee kinematic and kinetic variables between the groups. Results: There were no differences in sagittal- and frontal-plane knee angles between the groups ( P > .05 for all). The AH group demonstrated decreased tibial internal rotation during weight acceptance during gait ( P = .01) and increased tibial external rotation during jogging at initial contact ( P = .03) and during weight acceptance ( P = .02) compared with the SH group. In addition, the AH group demonstrated decreased peak negative knee power during midstance ( P = .01) during gait compared with the SH group, after controlling for gait speed, which differed between groups. Conclusion: Participants with hamstring strength asymmetry showed altered involved knee mechanics in the sagittal plane during gait and in the transverse plane during gait and jogging compared with those with more symmetric hamstring strength. Clinical Relevance: Hamstring strength asymmetry is common at 3 years after ACLR with a hamstring tendon autograft and affects involved knee mechanics during gait and jogging. Additional research is warranted to further investigate the longitudinal effect of these alterations on knee function and joint health after ACLR.