Single-leg triple hop propulsion strategies in females with and without a history of ACLR

Abstract

Context: The single-leg triple hop is a commonly used functional task following anterior cruciate ligament reconstruction (ACLR). However, recent research suggests that individuals may utilize a compensatory propulsion strategy to mask underlying quadriceps dysfunction and achieve symmetrical hop performance. Objective: Evaluate the performance and propulsion strategies employed by females with and without ACLR during a single-leg triple hop. Design: Cross-sectional. Setting: Laboratory. Patients or Other Participants: Thirty-eight females (ACLR=19, 19.2±1.8 years, 1.64±0.70m, 63.8±7.6 kg; Control=19, 21.1±3.3 years, 1.67±0.73m, 67.3±9.3 kg). Main Outcome Measure(s): Hop distance and limb symmetry index (LSI) were assessed during a single-leg triple hop for distance. Propulsion strategies were assessed during the first and second hops of the single-leg triple hop. Separate two-way ANOVA models were used to assess the influence of ACLR, joint and their interaction on mechanical joint work, moment impulse and the relative joint contributions to total work and impulse in females with and without a history of ACLR. Results: Despite achieving a mean LSI of ~96%, females with ACLR produced less total work in their reconstructed limb compared bilaterally during single-leg triple hop propulsion (First Hop: p=.002; Second Hop: p=.02). During the first and second hop, the reconstructed knee produced 19.3% (p=.03) and 27.3% (p=.001) less work compared bilaterally. No significant differences were identified between limbs in moment impulse (First Hop: p=.67; Second Hop: p=.76). Irrespective of limb or group, the ankle was the largest contributor to both work and moment during both first and second hops (p<.001). Conclusions: Clinicians should caution against using a single-leg triple hop as a surrogate for restored lower extremity function in females post-ACLR. This recommendation is driven by the compelling findings that knee joint deficits persist in the reconstructed limb despite achieving ~96% LSI and that regardless of previous injury status, single-leg triple hop propulsion is predominantly driven by the ankle.