Knee Joint Kinematic and Kinetic Asymmetries During Single Limb Landings Among Recreational Athletes With and Without a History of ACL Reconstruction Flannery E, SPT; Kraich L, SPT; Jenkins W, PT, DHS, LATC, ATC; Willson J, PT, PhD Human Movement Analysis Laboratory, Department of Physical Therapy, East Carolina University, Greenville NC INTRODUCTION RESULTS DISCUSSION Approximately 200,000 ACL injuries occur each year in the US (7) 1 in 17 patients sustain a second ACL injury within 2 years and 1 in 3.7 sustain a second ACL injury within 10 years of ACL reconstruction (ACLR) (8) Subjects demonstrate altered single and double limb landing mechanics in the involved limb post-ACL reconstruction Decreased peak knee flexion (1,10), knee flexion excursion (4), knee adduction (1), vertical ground reaction force (6), knee extension moment (3,4), and sagittal plane knee symmetry (5) Subjects after ACLR demonstrate higher peak tibiofemoral joint compressive forces during single limb drop-landing tasks when compared to healthy controls (9) No long term analyses of symmetry in jump landing mechanics between limbs among people with and without a history of ACLR Significant interactions were found between limb (involved versus uninvolved) and group (ACL versus healthy matched control) for: Peak knee flexion angle (p = 0.02), knee flexion excursion (p = 0.005), knee extension moment (p = 0.01), peak tibiofemoral joint anterior shear force (p = 0.002), knee proportion of support moment (p = 0.002) No significant interactions were found between limb and group for: Knee flexion at initial contact (p = 0.47), peak knee adduction angle (p = 0.095), knee adduction excursion (p = 0.18), peak knee abduction moment (p = 0.20), peak vertical ground reaction force (p = 0.48), peak tibiofemoral joint compression force (p = 0.10), total support moment (p = 0.17) Subjects after ACLR land with significantly decreased peak knee flexion, knee flexion excursion, peak knee extension moment, peak tibiofemoral anterior shear, and knee proportion of the support moment in the ACLR lower extremity No side-to-side differences within healthy control group Asymmetry between limbs was only apparent among ACLR participants Increased asymmetry in knee extension moments between limbs of people after ACLR increases the odds of a second ACLR(8) Neuromuscular integration deficits after ACLR may play a role in long term asymmetries at the knee during single limb landing tasks Cautious movement (quadriceps avoidance pattern) Increased hip and ankle strategies, demonstrating offloading of the knee during single limb landing Altered bilateral lower extremity movement patterns may be present after ACL reconstruction Altered neuromuscular recruitment patterns between limbs may develop, persist, and contribute to risk of reinjury Psychological components may contribute to single limb landing after ACL reconstruction, leading to straighter, stiffer landing mechanics on the reconstructed limb Figure 1. Peak knee flexion (degrees) during a single limb landing from a jump. Figure 2. Knee flexion excursion (degrees) during a single limb landing from a jump. PURPOSE Evaluate kinematic, kinetic, and support moment side-to-side symmetry at the knee between recreational athletes with and without a history of ACLR during single limb landing from a jump METHODS Participants 28 recreational athletes (18 females/10 males) Inclusion criteria: 2-7 years post ACL reconstruction, one involved lower extremity, 18 to 40 years old Exclusion criteria: surgery to contralateral lower extremity, injury to either lower limb limiting exercise in past two years 28 healthy matched controls (gender, body mass, Tegner) Procedure Maximum vertical jump determined using Vertec® Six jumps from bilateral stance to 75% of maximum vertical jump height, with single limb landing Analysis 31 reflective markers tracked with an 8-camera Qualysis (Gothenburg, Sweden) motion analysis system (240 Hz) Variables examined: C-motion software (Bethesda, MD) peak knee flexion knee flexion excursion peak knee extension moment peak vertical GRF peak TFJ anterior shear and compression (2) knee proportion of support moment Variable interactions between lower extremities and groups determined using two-way ANOVA during the first 60% of landing with the level of significance for all tests set at p < 0.05 Effect sizes examined using Cohen’s d LIMITATIONS Figure 3. Peak knee extension moment (Nm/kg*m) during a single limb landing from a jump. Figure 4. Peak tibiofemoral joint anterior shear force (BW) during a single limb landing from a jump. Subjects matched with respect to three variables only (gender, body mass, Tegner) Heterogeneity among subjects with ACL reconstruction Concurrent meniscus injury, graft type Recall bias/accuracy of information (no medical charts) Anticipatory activity versus reactionary sport-specific activity Group Peak Knee Flexion Knee Flexion Excursion Peak Knee Extension Moment Peak TFJ Anterior Shear Force Knee Proportion of Support Moment Between Limbs ACLR -.39 -.78 -.58 -.69 -.67 Control .08 -.07 .16 .12 .29 Negative values indicate smaller values in the involved limb Between Groups -.04 .51 -.01 .23 .55 Negative values indicate smaller bilateral values in the ACLR group CLINICAL RELEVANCE Addressing neuromuscular control deficits may be equally as important as strengthening in subjects after ACLR Focusing on “softer” landing strategies emphasizing increased peak knee flexion and knee flexion excursion during single limb landing may help to reduce incidence of reinjury in subjects after ACL reconstruction Figure 5. Knee proportion of support moment (%) during a single limb landing from a jump. Table 1. Effect sizes (Cohen’s d). Black = small effect; blue = moderate effect; red = large effect. REFERENCES Delahunt E, Sweeney L, et al. 2012. J Orthop Res 30: 72-78. DeVita P, Hortobagyi T. 2001. J Appl Biomech 17: 297-311. Ernst G, Saliba E, et al. 2000. Phys Ther 80: 251-260. Ithurburn MP, Paterno MV, et al. 2015. Am J Sport Med 43: 2727. Lepley L, Wojtys E, et al. 2015. Clin Biomech 30: 738-747. Paterno M, Ford K, et al. 2007. Clin J Sport Med 17: 258-262. Paterno M, Rauh M, et al. 2014. Am J Sport Med 42: 1567-1573. Paterno M, Schmitt L, et al. 2010. Am J Sport Med 38: 1968-1978. Tsai LC, McLean S, et al. 2012. J Orthop Res 30: 2007-2014. Xergia S, Pappas E, et al. 2013. J Orthop Sport Phys 43: 154-162.