Single-Legged Triple-Hop Propulsion Strategies in Females With and Those Without a History of Anterior Cruciate Ligament Reconstruction

Abstract

Context: The single-legged triple hop is a commonly used functional task after anterior cruciate ligament reconstruction (ACLR). Recently, researchers have suggested that individuals may use a compensatory propulsion strategy to mask underlying quadriceps dysfunction and achieve symmetric hop performance. Objective: To evaluate the performance and propulsion strategies used by females with and those without ACLR during a single-legged triple hop. Design: Cross-sectional study. Setting: Laboratory. Patients or Other Participants: A total of 38 females, 19 with ACLR (age = 19.21 6 1.81 years, height = 1.64 6 0.70 m, mass = 63.79 6 7.59 kg) and 19 without ACLR (control group; age = 21.11 6 3.28 years, height = 1.67 6 0.73 m, mass = 67.28 6 9.25 kg). Main Outcome Measure(s): Hop distance and limb symmetry index (LSI) were assessed during a single-legged triple hop for distance. Propulsion strategies were evaluated during the first and second hops of the single-legged triple hop. Separate 2-way analysis-of-variance models were used to examine the influence of ACLR, joint, and their interaction on mechanical joint work, moment impulse, and the relative joint contributions to total work and moment impulse in females with and those without a history of ACLR. Results: Despite achieving a mean LSI of approximately 96%, the ACLR group produced less total work in the reconstructed than the uninvolved limb during single-legged triple-hop propulsion (first hop: t18 = −3.73, P = .002; second hop: t18 = −2.55, P = .02). During the first and second hops, the reconstructed knee generated 19.3% (t18 = −2.33, P = .03) and 27.3% (t18 = −4.47, P, .001) less work than the uninvolved knee. No differences were identified between the involved and uninvolved limbs of the ACLR group in moment impulse (first hop: t18 = −0.44, P = .67; second hop: t18 = −0.32; P = .76). Irrespective of limb or group, the ankle was the largest contributor to both work and moment during both the first and second hops (P, .001). Conclusions: Clinicians should exercise caution when using a single-legged 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 persisted in the reconstructed limb despite an LSI of approximately 96% and, regardless of previous injury status, single-legged triple-hop propulsion was predominantly driven by the ankle.