Single leg hop for distance symmetry masks lower limb biomechanics: time to discuss hop distance as decision criterion for return to sport after ACL reconstruction?

Abstract

BackgroundWe evaluated the lower limb status of athletes after anterior cruciate ligament reconstruction (ACLR) during the propulsion and landing phases of a single leg hop for distance (SLHD) task after they had been cleared to return to sport. We wanted to evaluate the biomechanical components of the involved (operated) and uninvolved legs of athletes with ACLR and compare these legs with those of uninjured athletes (controls).MethodsWe captured standard video-based three-dimensional motion and electromyography (EMG) in 26 athletes after ACLR and 23 healthy controls during SLHD and calculated lower limb and trunk kinematics. We calculated lower limb joint moments and work using inverse dynamics and computed lower limb muscle forces using an EMG-constrained musculoskeletal modelling approach. Between-limb (within ACLR athletes) and between-group differences (between ACLR athletes and controls) were evaluated using paired and independent sample t-tests, respectively.ResultsSignificant differences in kinematics (effect sizes ranging from 0.42 to 1.56), moments (0.39 to 1.08), and joint work contribution (0.55 to 1.04) were seen between the involved and uninvolved legs, as well as between groups. Athletes after ACLR achieved a 97%±4% limb symmetry index in hop distance but the symmetry in work done by the knee during propulsion was only 69%. During landing, the involved knee absorbed less work than the uninvolved, while the uninvolved knee absorbed more work than the control group. Athletes after ACLR compensated for lower knee work with greater hip work contribution and by landing with more hip flexion, anterior pelvis tilt, and trunk flexion.ConclusionSymmetry in performance on a SLHD test does not ensure symmetry in lower limb biomechanics. The distance hopped is a poor measure of knee function, and largely reflects hip and ankle function. Male athletes after ACLR selectively unload the involved limb but outperform controls on the uninvolved knee.

Symmetry in Triple Hop Distance Hides Asymmetries in Knee Function After ACL Reconstruction in Athletes at Return to Sports

“…A recent in-depth assessment of biomechanical outcomes during a single-leg hop for distance revealed several kinematic and kinetic interlimb deficits and alterations after ACLR, despite adequate hop distance performance at RTS; that is, athletes after ACLR selectively unload the involved knee via hip and upper body kinematic adaptations. 22 In contrast, triple hop for distance in patients after ACLR has not been biomechanically evaluated, possibly because of the expensive equipment required to capture all 3 landings involved. During many sports, it is unusual for an athlete to be required to make a single movement, such as an isolated jump or hop.…”

Effect of an Anterior Cruciate Ligament Rupture on Knee Proprioception Within 2 Years After Conservative and Operative Treatment: A Systematic Review with Meta-Analysis

“…Although not assessed in the current meta-analysis, impaired proprioception in patients with ACLR might facilitate the occurrence of unfavorable knee positions during jumping or landing tasks, which are frequently incorporated in many return to sport protocols [80,81]. This hypothesis is supported by recent evidence demonstrating clear relationships between knee proprioception and landing kinematics by showing that individuals with higher levels of proprioception were able to better control knee flexion angles at initial contact during dynamic tasks [56].…”

Patellofemoral and tibiofemoral joint loading during a single‐leg forward hop following ACL reconstruction

“…10 Third, we did not collect hop-landing data for the uninjured limb of the ACLR group. A study of hop-landing biomechanics between the ACLR limb, uninjured contralateral limb and controls found differences across all pairwise comparisons, 15 due to adaptations specifically associated with the ACLR limb, rather than aberrant landing strategies inherent to the individual and more likely to manifest in both limbs. We similarly found biomechanical differences between the ACLR and uninjured contralateral limbs during running due to adaptations associated with the ACLR limb, 10 hence are confident that analogous between-limb differences would also be observed for hop-landing.…”

“…[4][5][6][7] Considerable differences between the ACLR limb compared to the contralateral limb and/or uninjured controls in joint kinematics and moments have been observed for tasks, such as walking, 8 running, 9,10 single-leg drop landing 11 and forward hop-landing. [12][13][14][15] The most evident and consistent differences for the ACLR limb are in the sagittal plane, 8 including a lower peak knee flexion angle and peak external knee flexion moment, 8 and increased overall leg stiffness. 12 These differences are apparent from 6 months after ACLR, 7,13 but persist for at least another 8 years, 16 suggesting lower-limb biomechanical function never fully recovers.…”